Add role name to Repo permissions level struct

[ankitsultania]

Fixes: #3189.

I am currently using this API to fetch what role does a user have on a repository. AFAICS, RepositoryPermissionLevel struct is missing role_name which is provided by the API (https://docs.github.com/en/rest/collaborators/collaborators?apiVersion=2022-11-28#get-repository-permissions-for-a-user). Due, to this I am unable to use the library. This PR introduces the field within the RepositoryPermissionLevel struct

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[gmlewis]

Thank you, @ankitsultania !
Please run step 4 found in CONTRIBUTING.md and push the auto-generated changes to this PR. Then, once the CLA is signed, we can merge.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 92.90%. Comparing base (2b8c7fa) to head (1370675).
Report is 70 commits behind head on master.

Additional details and impacted files

@@ Coverage Diff @@## master #3186 +/- ##
==========================================
- Coverage 97.72% 92.90% -4.82% 
==========================================
Files 153 171 +18 Lines 13390 11548 -1842 ==========================================
- Hits 13085 10729 -2356 - Misses 215 726 +511 - Partials 90 93 +3 

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[ankitsultania]

closing this out and will work on my other PR