Use PureComponent instead since it is a simple shouldComponentUpdate check now.

This reverts commit 97f8eb63, reversing
changes made to 2e017f06.

There was a useability issue discovered in testing where trying to trim a sound to be of zero length would fail, but just leave the trimmers active. Clear them out, since the trim is invalid

This is used because the sortable drop is also used for general dropping as well as sorting drop, so you need to be able to drop into a sortable list that does not contain any items.

Make the corresponding reorder code be more careful to check if there is a newIndex.

On slow machines it was possible to double click record before the chunk of samples had been processed, causing zero-length audio buffers

https://github.com/LLK/scratch-gui/pull/4312 had a function name conflict with the existing code. This change fixes that by renaming the conflicting function, and removes redundant code.

Move the onClick handler to the overlay wrapper so that the whole stage is clickable to start the project instead of just the green flag button

www needs to know when a project finishes loading so that remixing can be disabled while the project is in a state that cannot be remixed.

Browsers other than IE will be allowed to load the GUI.
However, if there is an error, the error boundary will display an unsupported browser message recommending they update to the latest version of a supported browser.

For the purposes of this PR, ‘supported’ means you can load the gui (anything other than IE), and recommended is just the browsers that meet our minimum requirements for Chrome, Firefox, Edge and Safari.

The playground now displays this on startup when in Scratch Desktop
simulation mode.

randomize sprite positions when added from image file or from library (through 'choose from library' and 'surprise')