Merge branch 'develop' into blockDrag

src/components/action-menu/action-menu.css

src/components/action-menu/action-menu.jsx

src/components/action-menu/icon--backdrop.svg

src/components/action-menu/icon--camera.svg

src/components/action-menu/icon--file-upload.svg

src/components/action-menu/icon--paint.svg

src/components/action-menu/icon--sprite.svg

src/components/action-menu/icon--surprise.svg

src/components/asset-button/asset-button.css

src/components/asset-button/asset-button.jsx

src/components/asset-panel/selector.css

src/components/asset-panel/selector.jsx

src/components/green-flag/green-flag.css

src/components/gui/gui.css

src/components/sprite-selector/sprite-selector.css

src/components/sprite-selector/sprite-selector.jsx

src/components/stage-selector/stage-selector.jsx

src/components/target-pane/target-pane.jsx

src/containers/costume-tab.jsx

src/containers/extension-library.jsx