Fix by disabling overflow scrolling when a modal is open (this prevents the scrolling input issue) and reducing the top margin on custom procedures because it is a taller modal than most

fixes #2983

* Fix all the little RTL layout bugs

- [ ] borders on toolbox and workspace mirror correctly
- [ ] spacing on stage selector is correct
- [ ] stage size icons are mirrored
- [ ] extension library coming soon text is positioned correctly
- [ ] only mirror blocks icon on the tab (others stay right-handed)
- [ ] drop down icon in create variable modal has correct spacing

* FIx RTL backpack header border-radius

* round the bottom corner of paint/sound editors

This makes the editor’s asset panels match the blocks.

padding and margin changes to make www project page layout work without hacks; hack to position monitors correctly

I think this switches all the icons we saw. I also switched the icons on the tabs (the blocks going the wrong way looked bad).

Correct margins for tabs, tab icons.

Goes along with https://github.com/LLK/scratch-blocks/pull/1646

Fixes #2448 (tab wrapping in Japanese). Also ensures that none of the Sprite info area wraps. Does not address the issue where the sprite info area is too big and pushes the stage info off the screen.

I don't love this solution, but I remember not being able to figure out a way to not specify the max width because it is needed in order for the flowing to work. Without the max-width, the sprite tiles try to be in a row, pushing over everything else.

* Player mode

Add isPlayerOnly property on GUI. Move isFullScreen into mode reducer with isPlayerOnly.

Full screen needs to be a separate prop so that GUI knows what to show when exiting full-screen (either player-only or full editor).

- set `gui-body * {box-sizing: border-box;}` instead of expecting it to be set by the enclosing component/playground, and removed uses of content-box (adjusting sizes as needed) 
- Added `!isPlayerOnly` to the conditions for draggable sprites
- rewrote player example to use player mode.

Updates include modifications to interaction states for the following: tabs, add menus, forms, and stage selector.

- Auditing color CSS and componet CSS to make consistent.
- Made a first pass of changes to increase contrast to elements that previously were problematic

Resolves https://github.com/LLK/scratch-gui/issues/1713

* Implement GH-830: Add coming soon tooltips

This implements coming soon tooltips for:
* the small stage size
* save, load and language

It also creates the component that can be copied over into the paint editor for use there as well.

Lastly, this does a small refactor on the full screen implementation to include multiple small screen sizes too.

I changed the color of the bottom of the tab when selected from white
to the background color of the block chooser.
The main reason for the change was that the white bottom on the tabs
did not blend well with the boundary between gray/blue and white when
selected.  It has been changed so that there is a line that is lighter
than the regular border color which signifies that the tab is selected
and gives it separation from the white content but doesn’t separate the
content too far from the tab as a darker color would do.

Alphabetize all the things

To show the "Add Extension" button, you must now add `?extensions` to
the URL used to load the GUI.

Add class name props to the components, and fix positioning for the green flag to be reusable.