Add reusable PR auto-labeler workflow

[pratikmankawde]

High Level Overview of Change

Adds a reusable workflow_call workflow that automatically applies/removes GitHub labels based on checked checkboxes in PR descriptions. This pairs with existing PR templates' "Type of Change" sections — no extra effort from contributors, labels stay in sync with the description.

Context of Change

Repos like rippled already have structured PR templates with checkbox fields (Type of Change, API Impact). This workflow parses those checkboxes and maps them to labels, eliminating manual label management.

How it works

1. Calling repo provides a JSON label_mapping input: {"- \\[x\\] Bug fix": "BugFix", ...}
2. Workflow regex-matches each pattern against the PR body
3. Checked boxes -> labels added; unchecked boxes -> labels removed

Example PR with effect: pratikmankawde#1
Try changing the 'type of change' options. The labels change automatically. Might take a-few seconds though.

Type of Change

• New feature (non-breaking change which adds functionality)

Files

• pr-auto-labeler.yml — the reusable workflow
• test-pr-auto-labeler.yml — test workflow with sample rippled mappings

[mathbunnyru]

This shouldn't be implemented manually.

If we agree to apply custom labels, it should be done via add_label + custom_labels of https://github.com/ytanikin/pr-conventional-commits

And if we decide to go this way, it should be done on top of #73, not as a separate workflow

[pratikmankawde]

This shouldn't be implemented manually.

If we agree to apply custom labels, it should be done via add_label + custom_labels of https://github.com/ytanikin/pr-conventional-commits

And if we decide to go this way, it should be done on top of #73, not as a separate workflow

I believe using ytanikin/pr-conventional-commits, is introducing a new workflow and some more expectation from developers. We can achieve what we want with the existing workflow.