* added account navigation menu, copied and adapted from www

* fixed css

* support for login menu, registration menu from www

* Dropdown replaced with MenuBarMenu, override www css in menus

* render and style login dropdown via function from www

* moved menu styling from menu itself to menu bar

* refactoring menu components and containers

* refactor and restyle account nav menu

* cleaned up cruft and css per rschamp's review of PR 3070

styling for title field; correct input target in tests; make download filename safer with default, max length; in playground index, correctly pass props through to gui container

Removing this was the point of moving the test up one level. Thanks @chrisgarrity, good catch!

If the VM is ever instantiated, which happens whenever GUI is instantiated due to default props, then IE11 will crash

* Don't show intro modal if hideIntro passed to PreviewModal

* Add hideIntro prop to GUI

* Move intro modal hiding logic into its own function

And implement toggle on player playground

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.

Also remove some obsolete code

Pass a `stageSize` property down from a centralized `MediaQuery` in the
GUI component, and control the size of the stage and all surrounding
elements based on that value. Note that this is a pure property and is
not stored in the Redux state, since we gain access to the results of
the media query during `render()` and we shouldn't change Redux state
during `render()`.

Some stage-adjacent elements don't yet react correctly to the smallest
stage size.

There will probably need to be more backpack config options in the future, so just make this a bit more future proof

* 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.

This reverts commit 29d5619d.

* WIP tips

* WIP first card stack

* WIP use tips reducer to show things to try

* single card deck similar to mask sequence

* collapse option

* Add zoom card

* WIP tips

* Reorganized to redux

* Add zooming to the gifs

* Blue cards + navigation

* Add tips to new nav bar

* Remove blue

* Update design with icons

* deck updates wip

* Updated card decks

* Add videos to libraries

* Update initial card and clicker preview

* Add backdrop to initial card step.

* WIP use vimeo player instead

* New simple spin deck

* Spin around and say hello decks

* Update button and sub-card styles

* Fix "tips" button in menu bar

* Use move cursor

* Fix cursor

* Use same image for deck preview and library

* Fix cursor again

* Update clicker game deck

* Add videos as single-step decks

* Change tips in menu bar to ? icon

* Change “tips” to “how-tos” in library

* Add help icon to cards

* Update deck library images

* Add drag cover for youtube video to prevent catching mouseup

* add a step to spin deck for clicking control

* Blue bar style updates

* Add step pips

* Update clicker game name to run away

* Fix image padding

* Add change color step to spin deck

* Add start sound step to run away deck

* Update say deck to start with adding a sprite

* Remove package lock

* Remove zooming functionality

* Remove unnecassary prototype changes

* Split up rendering of cards into smaller parts

* Use FormattedMessage for all strings

* Automatic lint fixes

* Almost finished with lint errors!

* Fix more lint errors

* Clean up CSS

* Fix webpack config

* Updates to preview modal for release

* Design tweaks and remove import modal

* Resolve issues with tests

* Copy edits HT Eric

* Resolve lint issue with integration test

* One more change to the disclaimer language

* Add line break

It seems like there is some kind of touch action interference coming
from the blocks panel, where if you touch the tabs on a touchscreen
chromebook/chrome responsive mode, it does not select the tab if the
touch radius is overlapping the blocks panel at all. See gifs in PR for
more explanation. Fixes issue #1283, making chromebooks useable!

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