Merge branch 'master' into volume

.vscode/tasks.json

docs/state/readme.md

docs/state/transforms.md

src/mol-canvas3d/controls/trackball.ts

src/mol-plugin/component.ts

src/mol-plugin/context.ts

src/mol-plugin/index.ts

src/mol-plugin/skin/base/components/controls.scss

src/mol-plugin/skin/base/components/misc.scss

src/mol-plugin/skin/base/components/slider.scss

src/mol-plugin/spec.ts

src/mol-plugin/state.ts

src/mol-plugin/state/animation/built-in.ts

src/mol-plugin/state/animation/manager.ts

src/mol-plugin/state/animation/model.ts

src/mol-plugin/ui/controls/common.tsx

src/mol-plugin/ui/controls/parameters.tsx

src/mol-plugin/ui/controls/slider.tsx

src/mol-plugin/ui/plugin.tsx

src/mol-plugin/ui/state-tree.tsx