* Change the title of some widget references to their class names
The widget reference index had a slight mixture of widget title styles, some
being their class name, others being "written English" type titles. This
settles on the titles always being the class name.
* Add a link to the ContentSwitcher to the widget gallery
No screenshot for this, on purpose. By definition this widget isn't visible,
except via other widgets that it's enclosing and handling.
* Have mkdocs watch the main nav file
* Mark the content switcher off the roadmap
A new form of Checkbox will be arriving in Textual soon, working in
conjunction with a RadioButton. What was called Checkbox is perhaps a wee
bit heavyweight in terms of visual design, but is a style of widget that
should remain.
With this in mind we're renaming the current Checkbox to Switch. In all
other respects its workings remains the same, only the name has changed.
Things for people to watch out for:
- Imports will need to be updated.
- Queries will need to be updated; special attention will need to be paid to
any queries that are string-based.
- CSS will need to be changed if any Checkbox styling is happening, or if
any Checkbox component styles are being used.
See #1725 as the initial motivation and #1746 as the issue for this
particular change.
