feat: Bun's C ABI FFI bindings

[fabrv]

Bun's C ABI FFI bindings (FFI^2)

[fabrv]

@zth @nojaf Please review 🙏

[Copilot]

Pull request overview

Adds initial ReScript bindings for Bun’s bun:ffi module (FFI^2) and introduces accompanying FFI-focused tests plus small C fixtures to validate dlopen, typed pointers, and cc compilation.

Changes:

• Add src/FFI.res bindings for bun:ffi (dlopen/linkSymbols, pointers, CString/JSCallback/CFunction, cc, viewSource, read helpers).
• Add a new FFI test suite and small C sources used by the tests.
• Add a precompiled test/ffi_testlib.so artifact for dlopen-based tests (plus bun.lock).

Reviewed changes

Copilot reviewed 6 out of 8 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
test/ffi_testlib.so	Adds a precompiled shared library used for dlopen tests.
test/ffi_testlib.c	C fixture implementing simple functions (add/multiply/etc.) for FFI tests.
test/ffi_square.c	C fixture for validating CC.compile from a file.
test/FFITest.res	ReScript FFI test suite exercising suffix/dlopen/cstring/pointers/read/cc.
test/FFITest.js	Generated JS output for the ReScript FFI test suite.
src/FFI.res	New bun:ffi bindings for ReScript, including Read, CString, JSCallback, and CC.
src/FFI.js	Generated JS output for the new FFI bindings module.
bun.lock	Adds a Bun lockfile snapshot.

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[nojaf]

@fabrv I think the remarks are on point, can you take a look.

[fabrv]

@nojaf Comments resolved. Please take another look. Thanks