Refresh workspace with sprite-specific blocks when sprite changes

Prevent deleting a sound from exploding

chore(package): update eslint-plugin-react to version 7.5.1

Make selector column responsive to paint editor width

Enable selection of sprite visibility by keyboard.

Show focus on language selector.

Hide icons from screenreader

This is for https://github.com/LLK/scratch-paint/pull/194, making the selector area smaller on tablet so as to create more space for the paint editor

Update all react 16.1.0 related dependencies together

Add alternate text for Scratch logo.

Wire up ask/answer components to the stage

Prevent switching tabs while one of these blocks is glowing from
crashing because it is given a new ID.

Use scratch-ll10n for extracting strings

Add music extension

Update enzyme-adapter-react-16 to the latest version 

Add aria label to language selector.

Add ask and answer blocks