Add cspell dictionary

[jjspace]

Description

These are some small repo changes that I've had locally for a little while and on't want to keep git-ignoring locally or stashing every PR

1. Add Code spell checker as a workspace recommended extension
2. Add .vscode/cspell.json to include a dictionary of words used in this project for the spell checker
3. Add @ts-expect-error in CesiumSandcastle because it's using the "wrong" require function and if you have JS Type checking on it flags the entire file
   

Code Spell Checker

Code spell checker is really helpful when coding to make sure variable names and strings are spelled correctly. Longer term we may want to add cspell as a CI or pre-commit check but right now there's too many words that would be flagged as incorrect to justify that effort. To that end I do want to push people to use the extension more and collectively, gradually build up the dictionary until we're at a point there are very few flagged words and using the cli is more seemless.

When a word is flagged you just have to put the cursor on it and trigger the VSCode suggestion window Ctrl+. for me. Then just make sure you select the cspell.json file to make sure it's added to the repo's dictionary instead of your user or workspace settings.

@ggetz I know we discussed this and I think you have a list of words already in your user settings, feel free to copy those over and commit to this branch if you have a bunch to add intantly

Issue number and link

Part of #11954

Testing plan

Not much to test.
You can try turning on JS type checking for the sandcastle if you want, just be aware there are still lots of other TS errors we have in the library.
Add the extension if you don't already have it and flag a word and make sure you understand how to add words to our dictionary.

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 update 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.

[ggetz]

@lukemckinstry Could you please review and work with @jjspace to get this over the finish line?

[jjspace]

I just pushed a couple more commits to add some more configuration and a command to actually run the CLI checker using npm run cspell. I did some small spelling fixes but I don't think it's worth trying to address them all at once. These should be fixed as people notice them in other PRs and eventually we will probably be able to set up automated checking with CI.

For our repo it gets a little tricky because we use a lot of acronyms and geospatial specific language that is not recognized. We can add more dictionaries to separate these into specific files if we want. I started with this for names but then realized it could be overkill so we should probably add them only as needed.

[lukemckinstry]

Looks good and works as intended. Currently npm run cspell generates >2400 warnings, which as you point out are mostly valid misspellings and/or technical terms. I agree we can do corrections or add words to the ignore list gradually over time after committing this PR.

This is such a big code base with so many words that I do have a slight worry we could have collisions between valid jargon we want to ignore versus spelling mistakes we want to catch. I guess the solution there is to be mindful not to assign variable/class names that are/resemble misspellings.

1. any plans to add this to the Contributor Guide docs?
2. is there a way to run this spell checker on certain files, such as files modified in a PR? That could be good to include in the docs as recommended practice.
3. Are you still working on other areas of this PR? If not, then once you answer 1 & 2 above I'm happy to approve.

[jjspace]

@lukemckinstry I added a little bit to the docs to point it out.

[lukemckinstry]

Thanks for adding docs. A few small items

• lets add Spelling with an anchor link to the table of contents
• I think the docs should say npm run ... , which in turn point to the script in package.json which uses npx ...

[lukemckinstry]

Suggested change

	- Using cspell optional while we build up the wordlist but may eventually be required as part of our git hooks and CI. See [this issue](https://github.com/CesiumGS/cesium/issues/11954) for an active status on that.
	- Using cspell is optional while we build up the wordlist but may eventually be required as part of our git hooks and CI. See [this issue](https://github.com/CesiumGS/cesium/issues/11954) for an active status on that.

[lukemckinstry]

Suggested change

	- Run `npx cspell -c .vscode/cspell.json [file path]` to check a specific file
	- Run `npm run cspell -c .vscode/cspell.json [file path]` to check a specific file