Rewrite Button to Typescript (#2984)

* Rename Button file

* Convert to TS

* Add debug warning helper

Fires `console.warn`, but only when the forum is in debug mode. Can help to inform extension developers of possible issues with their JS code.

* Simplify button content template

* Rewrite Button component

- Prefer `aria-label` over `title`
- Don't duplicate button content to `title` attribute
- Warn in debug mode if button has no accessible content
- Use modern JS/TS syntax (`||=`, spread, etc)

* Update to work with new Button component

* Update warning

Co-authored-by: Matt Kilgore <tankerkiller125@gmail.com>

* Fire warning in `oncreate`

* Format

* Make Button have extensible Attributes type via generics

* Update args type

* Update js/src/common/components/Button.tsx

Co-authored-by: Matt Kilgore <tankerkiller125@gmail.com>
Co-authored-by: David Sevilla Martin <me@datitisev.me>
Co-authored-by: Alexander Skvortsov <sasha.skvortsov109@gmail.com>

js/src/common/helpers/fireDebugWarning.ts

@@ -0,0 +1,16 @@
+/**
+ * Calls `console.warn` with the provided arguments, but only if the forum is in debug mode.
+ *
+ * This function is intended to provide warnings to extension developers about issues with
+ * their extensions that may not be easily noticed when testing, such as accessibility
+ * issues.
+ *
+ * These warnings should be hidden on production forums to ensure webmasters are not
+ * inundated with do-gooders telling them they have an issue when it isn't something they
+ * can fix.
+ */
+export default function fireDebugWarning(...args: Parameters<typeof console.warn>): void {
+  if (!app.forum.attribute('debug')) return;
+
+  console.warn(...args);
+}