[CHORE] Rename project

[aclist]

The following areas will need to be updated:

• Repository name (GitHub will redirect automatically to the new URL)
• README
• References to the string kes and KES in any descriptions in-app
• Main example image (splash image)
• Documentation
• Build scripts (insert masthead/metadata)
• For consistency's sake, variable and object names (a bit tricky, but nothing a global find-and-replace cannot fix)
• N.B. Check wording inside of mod manifests

Originally posted by @aclist in https://github.com/aclist/kbin-kes/discussions/318#discussioncomment-11873825

[aclist]

One thing I've been thinking about is that, while GitHub will redirect to the new repository if the name is changed, some of the dependent components of MES have filenames that would probably also be changed (e.g. kes.user.sj -> mes.user.js). This means that for anyone running a version <5.0.0, the auto-update logic would try to fetch content from URLs that would not exist anymore.

I'm not sure whether this should be treated as expected behavior (a totally breaking change), or if there should be some extra migration logic here for the (unspecified numbers of?) users still running the kbin version.