Convert Google Sheets to CMS Starter

[madebyisaacr]

Since releasing the CMS Starter, we are converting all of our CMS sync plugins to be based on it so they all have consistent logic, design, file names, CSS styles, etc.

I started converting Google Sheets to the CMS Starter here: #258
It's probably 80% done. You can connect your sheet and sync content, but there are still some bugs to fix and all updates that have been merged since that was last worked on need to be re-added.

Notion and Airtable have already been converted to the CMS Starter, so Google Sheets is the last one.