feat(services/github): add github contents support

[hoslo]

Part #4253

[hoslo]

@Xuanwo When disable create_dir, op.create_dir("test/") will report this error

{"message":"path cannot end with a slash","errors":[{"resource":"Commit","field":"path","code":"invalid"}],"documentation_url":"https://docs.github.com/rest/repos/contents#create-or-update-file-contents"}

[Xuanwo]

not updated.

[hoslo]

fixed

[Xuanwo]

When disable create_dir, op.create_dir("test/") will report this error

Sad, let's create test/.gitkeep instead.

[hoslo]

.gitkeep

Should we remove .gitkeep from the list return？

[Xuanwo]

Should we remove .gitkeep from the list return？

Yes, we can ignore .gitkeep (not remove)

[Xuanwo]

Thanks!