Implement new UI component for icons #230

- Introduce `AppIcon.vue`, offering improved performance over the
  previous `fort-awesome` dependency. This implementation reduces bundle
  size by 67.31KB (tested for web using `npm run build -- --mode prod`).
- Migrate Font Awesome 5 icons to Font Awesome 6.

This commit facilitates migration to Vue 3.0 (#230) and ensures no Vue
component remains tightly bound to a specific Vue version, enhancing
code portability.

Font Awesome license is not included because Font Awesome revokes its
right:

> "Attribution is no longer required as of Font Awesome 3.0"
>
> Sources:
>
> - https://fontawesome.com/v4/license/ (archived: https://web.archive.org/web/20231003213441/https://fontawesome.com/v4/license/, https://archive.ph/Yy9j5)
> - https://github.com/FortAwesome/Font-Awesome/wiki (archived: https://web.archive.org/web/20231003214646/https://github.com/FortAwesome/Font-Awesome/wiki, https://archive.ph/C6sXv)

This commit removes following third-party production dependencies:

- `@fortawesome/vue-fontawesome`
- `@fortawesome/free-solid-svg-icons`
- `@fortawesome/free-regular-svg-icons`
- `@fortawesome/free-brands-svg-icons`
- `@fortawesome/fontawesome-svg-core`

tests/shared/WaitForValueChange.ts

@@ -0,0 +1,17 @@
+import { WatchSource, watch } from 'vue';
+
+export function waitForValueChange<T>(valueWatcher: WatchSource<T>, timeoutMs = 2000): Promise<T> {
+  return new Promise<T>((resolve, reject) => {
+    const unwatch = watch(valueWatcher, (newValue, oldValue) => {
+      if (newValue !== oldValue) {
+        unwatch();
+        resolve(newValue);
+      }
+    }, { immediate: false });
+
+    setTimeout(() => {
+      unwatch();
+      reject(new Error('Timeout waiting for value to change.'));
+    }, timeoutMs);
+  });
+}