mol-plugin: highlight and selection on canvas helper

src/mol-geo/geometry/picking.ts

src/mol-model/loci.ts

src/mol-plugin/behavior/built-in/representation.ts

src/mol-plugin/context.ts

src/mol-plugin/ui/viewport.tsx

src/mol-plugin/util/canvas3d-identify.ts

src/mol-util/input/input-observer.ts