Developer Docs: Centralize GitHub Actions in the `.github` repo

[palisadoes]

Objective

1. This task involves refactoring the .github/workflows/ workflows listed below to be located in our centralized repository at:
   • https://github.com/PalisadoesFoundation/.github/tree/main/.github/workflows
2. The contents of the files must exclusively reference he centralized versions in that repository

.github/workflows/auto-assign.yml
.github/workflows/issue-assigned.yml
.github/workflows/issue-unassigned.yml
.github/workflows/issue.yml
.github/workflows/pull-request-target.yml
.github/workflows/stale.yml
.github/workflows/pull-request-review.yml

1. All tests must pass and be valid
2. No other functionality must be affected

Related Issues

1. API: Centralize GitHub Actions in the .github repo talawa-api#4185
2. Mobile: Centralize GitHub Actions in the .github repo talawa#3220
3. Admin: Centralize GitHub Actions in the .github repo talawa-admin#5981
4. Plugin: Centralize GitHub Actions in the .github repo talawa-plugin#152
5. Talawa Docs: Centralize GitHub Actions in the .github repo talawa-docs#1103
6. Developer Docs: Centralize GitHub Actions in the .github repo #122
7. .github: Centralize GitHub Actions in the .github repo .github#7

[palisadoes]

@yashgoyal0110

[github-actions]

This issue did not get any activity in the past 10 days and will be closed in 360 days if no update occurs. Please check if the develop branch has fixed it and report again or close the issue.