Improve the documentation on how to release the widget #11876

It’s currently a bit difficult for Mendix devs to find clear instructions on how to properly release a widget. We’ve noticed a recurring issue where widgets are being added to UI modules using dev builds. Some widgets ended up being more than few mbs just because of it. Some devs are simply not aware of release build. We’re looking for ways to avoid this.

The only place this is currently documented is under the React Client reference.

I think it might be more beneficial to have it here as well in the Pluggable Widgets 'How-to' where it's more visible.

I’m happy to put a PR together for this if you think it’s a good idea!