🧠 Widget catalog replacement brainstorm

Now that the Flutter Gallery is no longer maintained, the widget catalog is the only way to quickly browse Flutter's core widgets to get a rough idea of what is available and what each looks like.

However, the current widget catalog is out of date, isn't easy to maintain, isn't super visually interesting or interactive, and isn't easy to dive in to.

We need a low-maintainence solution that:

- Helps Flutter developers discover widgets relevant to their needs.
- Doesn't include non-key/otherwise distracting widgets or allows hiding them.
- Doesn't duplicate content from API docs, use from there if needed.
- (Mostly) Automatically updated, at least for the stable channel.
- (Preferably) Allows developers to view an example of the widget or a visualization of it.

Please respond with any thoughts or proposals, both big or small. Web-based, Flutter-based, or mixed options are all possibilities.