Added eslint. To lint, npm run lint.

Linted the entire project. Using different rules for the script files
as there are a lot of undefined variables just because of the way the
DOM's global scope works.

Mostly just code cleanup, however the linter did catch a minor bug with
a settings regex. That has been corrected.

app/assets/js/discordwrapper.js

@@ -1,6 +1,5 @@
 // Work in progress
 const {Client} = require('discord-rpc')
-const ConfigManager = require('./configmanager')
 
 let client
 let activity