git_repo_check.R needs to be functionalized and added to ottrpal

[cansavvy]

What needs to be done:
git_repo_check.R needs to be functionalized and added to the ottrpal package (along with a unit test).

It's currently run like this in the transfer-rendered-files.yml github action.

Basically a repo is given and some creds and it just checks whether that repo exists.

Rscript --vanilla git_repo_check.R --repo "$GITHUB_REPOSITORY"  --git_pat "$GH_PAT"

This change in the ottrpal package would need to be updated in the base_ottr image
Then this job in the transfer-rendered-files.yml needs to be updated to use the base_ottr image and the new ottrpal function.