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