feat: Add Credentials Revoke API

[cointem]

Fixes: #3846.

This pull request introduces a new service for managing credentials in the GitHub API client, specifically adding support for revoking credentials via the API. The changes include a new service implementation, comprehensive unit tests, and integration of the service into the main client.

New Credentials Service Integration:

• Added the CredentialsService to the client, allowing users to revoke a list of credentials (tokens) through the new Revoke method in github/credentials.go.
• Registered CredentialsService in the Client struct and initialized it in the client setup, ensuring it is available for use. [1][2]

Testing Improvements:

• Added a new test TestCredentialsService_Revoke in github/credentials_test.go to verify correct request formation, response handling, and error cases for credential revocation.

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 92.43%. Comparing base (3afe183) to head (74ae15b).
⚠️ Report is 1 commits behind head on master.

Additional details and impacted files

@@ Coverage Diff @@## master #3847 +/- ##
=======================================
Coverage 92.42% 92.43% =======================================
Files 197 198 +1 Lines 14167 14175 +8 =======================================
+ Hits 13094 13102 +8 
Misses 884 884 Partials 189 189 

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[cointem]

refs #3846

[gmlewis]

Thank you, @cointem!
LGTM.
Awaiting second LGTM+Approval from any other contributor to this repo before merging.

cc: @stevehipwell - @alexandear - @zyfy29

[gmlewis]

Thank you, @alexandear!
Merging.