Format/slightly modernize the JS (#345)

* add basic JS tooling

* fix accidental uses of global variables

* auto-format

* add and fix a couple more standard lint rules

* remove useless return false from settimeout callbacks

* document JS contributing

* fix whitespace in package.json

* add JS stuff to codespell skiplist

* codespell take two

* update github action and add comments about duplicated logic

.gitignore

@@ -5,4 +5,7 @@ __pycache__
 db.sqlite3
 
 # vscode custom conf
-.vscode
+.vscode
+
+# JavaScript stuff
+node_modules