Gallery conversion for Sandcastle v2

[jjspace]

Description

This is inherently a big PR. We have over 250 sandcastle examples and in the new format they are each 4 files. To help facilitate review I've intentionally broken the change into 3 commits

1. Creating the conversion script itself
2. Running the conversion directly and ignoring any errors
3. Fixing all eslint issues in the sandcastles

This should hopefully make reviewing easier but it also should help with running the script again later if we need to. I know there's a chance new sandcastles get created or updated outside this effort. We will do a final content pass later to give them all a final cleanup but for now it should be mostly automated. I'm leaving the script in the repo for now but plan to remove it as well once we can make the switch.

Issue number and link

Part of #12566

Testing plan

• either run npm run dev from the sandcastle package or npm run build-sandcastle and npm start from the repo root
• Scroll through the gallery and make sure all items show up (UI changed drastically in Sandcastle using Stratakit #12731)
• Click on a handful of gallery items and make sure they work. lmk if you find broken ones but we will do a full pass on them all later.

Author checklist

• I have submitted a Contributor License Agreement
• I have added my name to CONTRIBUTORS.md
• I have updated CHANGES.md with a short summary of my change
• I have added or updated unit tests to ensure consistent code coverage
• I have updated the inline documentation, and included code examples where relevant
• I have performed a self-review of my code

[github-actions]

Thank you for the pull request, @jjspace!

✅ We can confirm we have a CLA on file for you.

[jjspace]

There were a number of sandcastles that follow this structure of defining multiple examples and assigning them to variables that never actually get used. I thought about disabling no-unused-vars for all sandcastles but I do think it's a valid error we want to avoid. Instead I disabled it for these files specifically. I do think it's handy to have examples like these so it's easy for people to play with them if they want.