GitHub.jl lacks validation for user-provided fields

GitForge.jl is a unified interface for interacting with Git "forges." Versions prior to 5.9.1 lack input validation of input validation for user-provided values in certain functions. In the `GitHub.repo()` function, the user can provide any string for the `repo_name` field. These inputs are not validated or safely encoded and are sent directly to the server. This means a user can add path traversal patterns like `../` in the input to access any other endpoints on `api.github.com` that were not intended. Users should upgrade immediately to v5.9.1 or later to receive a patch. All prior versions are vulnerable. No known workarounds are available.