Rework repo for managing multiple themes

[BeardedBear]

Hi Strealos!

I've reworked the repo to allow several things:

• I've fixed the typing problems
• I've restructured the whole thing to allow each theme to be well separated so as not to overwrite everything when you want to make a new one, each theme becoming a sort of miniature React app. (there's still a lot I'd like to share, but step by step haha)
• I've created a little script in node that creates a folder with the name selected in the themes folder, editing the package.json to add the script command. Don't bite me, I did it with my meager knowledge of Node!
• I added a little toggle for the dark theme, that's handy! (Although I did it on the fly with a custom event, but it works haha)

Edit: if you want to test, just follow the Readme, with npm install then npm run create-theme then npm run dev:<name of theme created>