Update .gitignore

[matthew-white]

This PR updates .gitignore to more closely match the .gitignore that ships with Vite (related: #671).

Before submitting this PR, please make sure you have:

• [x] run npm run test and npm run lint and confirmed all checks still pass OR confirm CircleCI build passes
• [x] verified that any code or assets from external sources are properly credited in comments or that everything is internally sourced