449 check client urls

[davidsmejia]

Same as before, but will merge after the new homepage changes are up.

Purpose

• adds an Rscript that takes a single argument ( destination of a json file that lists urls ) and checks if the files and section id exists
• adds a github action that calls the above script on PR's merging into the master branch with a url pointing to refinebio-frontend production list of refinebio-examples' urls

For any subsequent PRs, their checks will fail and present a list of the missing files and ids that correspond to any would be broken link. In order to pass you can request changes on the refinebio-frontend and rerun the Check Refinebio Frontend Urls action after the updates are deployed to get a passing result.

Issue addressed

449

Gotchas the reviewer should know about

The order of PRs that should be merged would be

• https://github.com/AlexsLemonade/refinebio-examples/pull/457
• https://github.com/AlexsLemonade/refinebio-frontend/pull/945
• this PR

Remaining concerns and questions

I think logistically an improvement would be for the action to run both on master and staging prs to match against refinebio-frontend master or dev branch so staging so they could both be deployed at the same time.

[davidsmejia]

Task failed successfully:

Please verify that the following file(s) exist:
index.html#this-should-fail
Error: Process completed with exit code 1.