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

package.json

@@ -0,0 +1,17 @@
+{
+  "private": true,
+  "scripts": {
+    "lint": "eslint 'tubearchivist/static/**/*.js'",
+    "format": "prettier --write 'tubearchivist/static/**/*.js'"
+  },
+  "devDependencies": {
+    "eslint": "^8.26.0",
+    "prettier": "^2.7.1",
+    "eslint-config-prettier": "^8.5.0"
+  },
+  "prettier": {
+    "singleQuote": true,
+    "arrowParens": "avoid",
+    "printWidth": 100
+  }
+}