Tested with `HSlider` and has basic support for other widget types, but I'm only adding support for what I'm immediately using or can access via the editor.
This can barely be called "support." It reads all text as a single block. I'd like to at least be able to unfocus the `TextEdit`, but it's going to require a custom key. Ctrl-tab and Ctrl-shift-tab seem like good candidates, but the editor grabs those already.
Moving through every focusable widget by tab/shift-tab is very slow. This commit introduces the concept of groups--widgets that can be skipped through via ctrl-tab/ctrl-shift-tab.
Right now this only includes containers where all children are focusable, but I'll expand the definition of groups over time to make navingating to large areas of the UI easier..
When we unfocus, wait a second. If we don't have focus after the timer elapses, warp the mouse to the global coordinates.
This seems to restore some semblance of focus whenever it is unset, while not breaking the case where a focus is set and the mouse suddenly jumps, thus changing the focus again.
Here I add a `ScreenReader` `Node` which, when added to the `SceneTree`, should read the contents of any supported `Control`. I also do a bit of cleanup on filenames, as well as breaking the editor plugin support into its own class.
* It was the mouse warping, not the grabbing of focus, that caused keyboard traversal issues. Now we only mouse-warp prior to simulating a right-click via Menu.
* Despite what the docs say, `id_focused` seems to pass an index, not an ID. Now popup menu items speak more accurately.
I'm not immediately sure how to present multiple tree selections. I also don't know if I can control selection status from the input events. So, for the time being, we force a single row to be selected. This isn't the most ideal solution, but it makes debugging other issues easier, so I'll use it for now to unblock other work.
