feat: add community contribution labeling workflow

[iamshobhraj]

Description

Add GitHub Actions workflow to automatically manage the "community-contribution-in-progress" label on issues based on external contributor assignments. This PR implements the workflow part that calls the shared action from learningequality/.github repository.

Issue addressed

Addresses learningequality/kolibri#12923

Changelog

• Description: Add automated workflow for managing community contribution labels when issues are assigned/unassigned to external contributors
• Products impact: none
• Addresses: Create a new GitHub action that adds/removes "community-contribution-in-progress" label on issues kolibri#12923
• Components: -
• Breaking: no
• Impacts a11y: no
• Guidance: -

Steps to test

1. Assign any issue to someone
2. Verify the community contribution label is automatically added
3. Unassign the issue
4. Verify the label is automatically removed

(optional) Implementation notes

At a high level, how did you implement this?

Added a workflow file that:

• Triggers on issue assignment/unassignment
• Uses the shared labeling action from learningequality/.github repository
• Configures proper authentication using workflow PAT

Testing checklist

• Contributor has fully tested the PR manually
• If there are any front-end changes, before/after screenshots are included (N/A)
• Critical and brittle code paths are covered by unit tests
• The change is described in the changelog section above

Reviewer guidance

• Is the code clean and well-commented?
• Are there tests for this change?
• Are all UI components LTR and RTL compliant (if applicable)?
• Add other things to check for here

After review

• The changelog item has been pasted to the CHANGELOG.md

Comments

[MisRob]

@rtibbles In this repo we don't yet have LE_BOT_APP_ID and LE_BOT_PRIVATE_KEY. Would you please set them before we merge?