Upgrade to Gatsby 4 and fix images paths that broke builds

[rogermparent]

I decided to use Gatsby 3 in #2447 since Gatsby 4 was still in beta, most plugins hadn't updated to match it, and it seemed to be a bit less stable in Heroku builds.

Since then, Gatsby 4 has left beta and most plugins have updated to work with it. Also, Gatsby Cloud's image processing has integrations specific to 4, so this PR will be used to test on Gatsby Cloud.

Also, it seems one of the upgrades since then has made it to that builds fail when an image path isn't found- this is a good thing, since we had a few images that were completely broken and just unnoticed, and some "phantom" images that worked when they shouldn't have.

This PR also updates the typescript and eslint packages, which was required because react-use uses named tuples, a feature introduced in newer TypeScript versions, and eslint needed to be upgraded alongside TypeScript.
I also upgraded stylelint, which then discovered a whole ton of CSS problems that we had before, including obvious stuff like duplicated keys. The results of stylelint --fix ended up being the bulk of the PR's diff.

[julieg18]

Looks great!

I noticed that the cards in the Doc's home page is styled differently:

I have no idea why though 🤔

[rogermparent]

@julieg18 Great catch on the card collapsing! I'm not sure why that would have changed, I know the major upgrade on github-markdown-css caused some issues, but I don't see how it would cause this completely custom flex setup to start breaking down.

I just fixed it by using slightly more proper margin-based spacing, though I had to apply it vertically to cardWrappers and horizontally to cards, it wouldn't work otherwise.

[rogermparent]

Not sure why Restyled is trying to change this, running format-all locally doesn't apply any changes, and the changes restyled is asking for cause lint-ts to break.

[julieg18]

Not sure why Restyled is trying to change this, running format-all locally doesn't apply any changes, and the changes restyled is asking for cause lint-ts to break.

I think I had the same issue when I tried to edit that particular file that Restyled is trying to restyle. I think it had something to do with the kind of environment that Restyled is using to run code.

[rogermparent]

I took a check around all the top-level pages and usages of the cards custom component, I haven't caught anything obvious. Willing to give this time for another once-over to be extra sure, but I think we're ready to send this in (and probably deal with some link check errors 😭)

[julieg18]

Looks good!