feat: allow custom formatjs_cli toolchain (#24)

### TL;DR

Add support for custom FormatJS CLI versions with a new example demonstrating how to use version 0.1.0.

### What changed?

- Enhanced the FormatJS CLI module extension to support custom binary versions
- Added a new `formatjs_repositories` attribute to the `toolchain()` tag that accepts custom URLs and SHA256 checksums
- Created a new example in `examples/custom_version/` demonstrating how to use a custom FormatJS CLI version (0.1.0)
- Removed version 0.1.0 from the built-in versions list to demonstrate the custom version feature
- Added `.lock` files to linguist-generated in `.gitattributes`

### How to test?

1. Navigate to the custom version example:
```bash
cd examples/custom_version
```

2. Build and test the example:
```bash
bazel build :messages
bazel test :test_extraction
bazel test :test_cli_version
```

3. Examine the extracted messages:
```bash
cat bazel-bin/messages.json
```

### Why make this change?

This change provides flexibility for users who need to:
- Test unreleased or pre-release versions of FormatJS CLI
- Use custom builds or patched versions
- Support platforms not yet in the official releases
- Pin to specific versions for compatibility reasons

The new API is inspired by the `rules_nodejs` pattern, making it familiar and easy to use for developers already working with Bazel JavaScript rules.

Author: longlho

.gitattributes

@@ -9,3 +9,4 @@ examples export-ignore
 # Occasionally there's a need to "stamp" the release version into a file
 # See https://blog.aspect.build/releasing-bazel-rulesets-rust for details if you need this.
 # formatjs/version.bzl export-subst
+*.lock linguist-generated

MODULE.bazel.lock

@@ -0,0 +1,67 @@
+"""Example BUILD file demonstrating extraction with custom FormatJS CLI version."""
+
+load("@rules_formatjs//formatjs:defs.bzl", "formatjs_extract")
+load("@rules_shell//shell:sh_test.bzl", "sh_test")
+
+# Simple TypeScript/React file with FormatJS messages
+genrule(
+    name = "generate_source",
+    outs = ["App.tsx"],
+    cmd = """cat > $@ << 'EOF'
+import { FormattedMessage, defineMessages } from 'react-intl';
+
+const messages = defineMessages({
+  welcome: {
+    id: 'app.welcome',
+    defaultMessage: 'Welcome to the custom version example!',
+    description: 'Welcome message on homepage',
+  },
+  goodbye: {
+    id: 'app.goodbye',
+    defaultMessage: 'Goodbye!',
+    description: 'Farewell message',
+  },
+});
+
+export function App() {
+  return (
+    <div>
+      <h1><FormattedMessage {...messages.welcome} /></h1>
+      <p><FormattedMessage {...messages.goodbye} /></p>
+      <FormattedMessage
+        id="app.inline"
+        defaultMessage="This is an inline message"
+        description="Inline message example"
+      />
+    </div>
+  );
+}
+EOF
+""",
+)
+
+# Extract messages using the custom FormatJS CLI version (0.1.0)
+# This demonstrates that custom platform configurations work correctly
+formatjs_extract(
+    name = "messages",
+    srcs = [":App.tsx"],
+    out = "messages.json",
+)
+
+# Test that we can read the extracted messages
+sh_test(
+    name = "test_extraction",
+    srcs = ["test_extraction.sh"],
+    data = [":messages"],
+)
+
+# Test that verifies we're using the custom CLI version (0.1.0)
+# This test accesses the CLI binaries directly to check their version
+sh_test(
+    name = "test_cli_version",
+    srcs = ["test_cli_version.sh"],
+    data = [
+        "@formatjs_v0_1_0_darwin_arm64//:cli",
+        "@formatjs_v0_1_0_linux_x64//:cli",
+    ],
+)

examples/aggregate/MODULE.bazel.lock

@@ -0,0 +1,54 @@
+"""Example demonstrating custom FormatJS CLI version configuration.
+
+This example shows how to use a custom version (0.1.0) that is not in the built-in
+FORMATJS_CLI_VERSIONS dictionary. This is useful for:
+- Testing unreleased versions
+- Using custom builds
+- Supporting platforms not yet officially supported
+"""
+
+module(name = "custom_version_example")
+
+bazel_dep(name = "rules_formatjs", version = "")
+bazel_dep(name = "rules_shell", version = "0.3.0")
+
+# Use local override since we're developing rules_formatjs
+local_path_override(
+    module_name = "rules_formatjs",
+    path = "../..",
+)
+
+# Configure custom FormatJS CLI version 0.1.0
+# This version was removed from the built-in versions but we can still use it
+formatjs_cli = use_extension("@rules_formatjs//formatjs_cli:extensions.bzl", "formatjs_cli")
+
+# Single toolchain call with custom binaries (similar to rules_nodejs pattern)
+formatjs_cli.toolchain(
+    name = "formatjs_v0_1_0",
+    formatjs_repositories = {
+        "0.1.0.darwin-arm64": [
+            "https://github.com/formatjs/formatjs/releases/download/formatjs_cli_v0.1.0/formatjs_cli-darwin-arm64",
+            "9b2c736b48cc65e763cf19ac7c190e527f9a8d4aa0798185e602f58becb99feb",
+        ],
+        "0.1.0.linux-x64": [
+            "https://github.com/formatjs/formatjs/releases/download/formatjs_cli_v0.1.0/formatjs_cli-linux-x64",
+            "884b9a41b9f6be649ea72277ebf22af0146043466d2ab94b28a57f95ffb7da1a",
+        ],
+    },
+)
+
+# Repository names are: {name}_{platform} and {name}_toolchains
+# Examples: formatjs_v0_1_0_darwin_arm64, formatjs_v0_1_0_linux_x64, formatjs_v0_1_0_toolchains
+use_repo(
+    formatjs_cli,
+    "formatjs_v0_1_0_darwin_arm64",
+    "formatjs_v0_1_0_linux_x64",
+    "formatjs_v0_1_0_toolchains",
+)
+
+# Register the custom version toolchains (0.1.0)
+# Note: Standard toolchains (0.1.2) are already registered by rules_formatjs root MODULE.bazel
+# Bazel will select the appropriate one based on platform constraints and registration order
+register_toolchains(
+    "@formatjs_v0_1_0_toolchains//:all",
+)