Replace all instances of yomichan

[koiyakiya]

This PR replaces (to my knowledge) every instance of yomichan to yomitan in the project (that is necessary). I ran the tests and they gave back no errors. I did a little testing and everything seems to work.

Some things to note:

• One problem I did have was exporting or importing dictionary collections, but the error it gave back probably has to do with me not setting up the enviornment right (it gave a TypeError: Dexie is not a constructor).
• Also, in the Errors tab in chrome extensions, it gives an Uncaught SyntaxError: Cannot use import statement outside a module, and links js/language/text-scanner.js:19 (anonymous function). Don't really know what this means...
• Other than that, Anki works, dictionaries import correctly, audio works, formatting is normal, etc. (Only tested on chrome)
• In templates.md, I changed the handlebars examples to yomitan. For example, {{~concat "yomitan_" (get "index") "_value"}}. I'm not sure if this is intended and if it is correct in the code.

If I did something wrong, please tell me, as this is my first time making a PR of this size...

(also the participant aiborii is just me, I think I messed with git a bit...)

[github-actions]

⚠️ Visual differences introduced by this PR; please validate if they are desirable.

View Playwright Report (note: open the "playwright-report" artifact)

[jbukl]

⚠️ Visual differences introduced by this PR; please validate if they are desirable.

View Playwright Report (note: open the "playwright-report" artifact)

just noting the playwright tests didn't actually fail - it's just detecting the title of the test page changing to yomitan
and the "Cannot use import statement outside a module" should be unrelated - I opened a PR regarding that
same with dexie