Enable linting of JS inside templates (#13708)

Indentation-related rules are disabled because indent templates with
tabs but our lint rules expect spaces.

Also had to exclude a few files where using template variables in the JS
is causing syntax errors for the JS parser. I don't think there's a way
to solve this otherwise.

Co-authored-by: Lauris BH <lauris@nix.lv>

package.json

@@ -55,6 +55,7 @@
   },
   "devDependencies": {
     "eslint": "7.13.0",
+    "eslint-plugin-html": "6.1.1",
     "eslint-plugin-import": "2.22.1",
     "eslint-plugin-unicorn": "23.0.0",
     "eslint-plugin-vue": "7.1.0",