Run linters on code and fix mistakes that are found

[misaugstad]

@uditpatwal added linters in PR #2430 for JavaScript, CSS, and HTML. I want to personally go through and run the linters on all of the code, make the necessary changes that can't be done automatically, and make sure that everything still works properly. After I've done that, we can make linting into a part of the PR submission process, where we should run the linter before pushing our code to Github. Similarly, we can use Github actions to lint, which will visually show errors brought up by the linter on the PR on Github (issue #2423 PR #2426).

I just want to wait until there are no large open PRs out there so that I don't add a million merge conflicts for people by doing this. Or I could even do this in two parts, where I lint the code that I'm pretty sure no one is currently working on. Then when those PRs are wrapped up, I do round two.