When `standalone` is set to true, this action button will only appear in
"standalone PWA" mode (e.g. home-screen mobile apps, or installed PWA on
desktop). Useful to e.g. only show forward and backward buttons. These
forward and backward buttons are now also added to the default action
button config.
Refactor Library/Std into subfolders for APIs, Infrastructure, Editor,
Widgets, etc. Add more documentation and descriptions. Update references
throughout website and docs.