docs: Add change-pr-state automation action documentation (#839)

* docs: Add change-pr-state automation action documentation

- Add change-pr-state action to overview list
- Document action parameters and usage
- Include example for converting draft PRs to ready for review
- Supports GitHub and GitLab platforms

Relates to LINBEE-21553

* docs: Add explicit triggers requirement note for change-pr-state

- Add informational note explaining gitStream doesn't run on draft PRs by default
- Link to execution model documentation for explicit triggers
- Update example comment for clarity

Since gitStream does not evaluate draft PRs by default, users must
configure explicit triggers (using the 'on' parameter) for automations
that use the change-pr-state action to function properly.

Author: vim-zz

docs/automation-actions.md

@@ -28,6 +28,7 @@ For all other actions, gitStream executes the actions in the order they are list
 - [`add-reviewers`](#add-reviewers) :fontawesome-brands-github: :fontawesome-brands-gitlab: :fontawesome-brands-bitbucket:
 - [`add-thread`](#add-thread) :fontawesome-brands-gitlab:
 - [`approve`](#approve) :fontawesome-brands-github: :fontawesome-brands-gitlab: :fontawesome-brands-bitbucket:
+- [`change-pr-state`](#change-pr-state) :fontawesome-brands-github: :fontawesome-brands-gitlab:
 - [`close`](#close) :fontawesome-brands-github: :fontawesome-brands-gitlab: :fontawesome-brands-bitbucket:
 - [`code-review`](#code-review) :fontawesome-brands-github: :fontawesome-brands-gitlab: :fontawesome-brands-bitbucket:
 - [`describe-changes`](#describe-changes) :fontawesome-brands-github: :fontawesome-brands-gitlab: :fontawesome-brands-bitbucket:
@@ -261,6 +262,36 @@ automations:
       - action: approve@v1
 ```
 
+#### `change-pr-state` :fontawesome-brands-github: :fontawesome-brands-gitlab:
+
+This action, once triggered, updates the PR state between draft and ready for review.
+
+!!! note "Explicit Triggers Required for Draft PRs"
+    Since gitStream does not run on draft PRs by default, this action requires the use of [explicit triggers](execution-model.md#explicit-triggers) to function properly. Define triggers using the `on` parameter at the automation level to specify when the automation should evaluate draft PRs.
+
+<div class="filter-details" markdown=1>
+
+| Args | Usage | Type | Description |
+| --- | --- | --- | --- |
+| `draft` | Optional | Bool | When `true`, convert the PR to Draft. When `false`, mark the PR as Ready for review. |
+
+</div>
+
+```yaml+jinja title="example"
+automations:
+  ready_for_review:
+    # Explicit triggers required to work with draft PRs
+    on:
+      - label_added
+      - pr_created
+    if:
+      - true
+    run:
+      - action: change-pr-state@v1
+        args:
+          draft: false
+```
+
 #### `close` :fontawesome-brands-github: :fontawesome-brands-gitlab: :fontawesome-brands-bitbucket:
 
 This action, once triggered, closes the PR without merging.