Add typescript guideline and typescript-specific eslint plugins and fix issues (#31521)

1. Add some general guidelines how to write our typescript code
2. Add `@typescript-eslint/eslint-plugin`, general typescript rules
3. Add `eslint-plugin-deprecation` to detect deprecated code
4. Fix all new lint issues that came up

web_src/js/utils/dom.js

@@ -270,7 +270,7 @@ export function replaceTextareaSelection(textarea, text) {
 
   textarea.contentEditable = 'true';
   try {
-    success = document.execCommand('insertText', false, text);
+    success = document.execCommand('insertText', false, text); // eslint-disable-line deprecation/deprecation
   } catch {
     success = false;
   }