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>

Makefile

@@ -312,7 +312,7 @@ lint: lint-frontend lint-backend
 
 .PHONY: lint-frontend
 lint-frontend: node_modules
-	npx eslint --max-warnings=0 web_src/js build webpack.config.js
+	npx eslint --max-warnings=0 web_src/js build templates webpack.config.js
 	npx stylelint --max-warnings=0 web_src/less
 
 .PHONY: lint-backend