wip, repr provider

src/apps/canvas/component/structure-view.tsx

src/apps/canvas/component/volume-view.tsx

src/mol-repr/representation.ts

src/mol-repr/shape/representation.ts

src/mol-repr/structure/complex-representation.ts

src/mol-repr/structure/registry.ts

src/mol-repr/structure/representation/ball-and-stick.ts

src/mol-repr/structure/representation/cartoon.ts

src/mol-repr/structure/units-representation.ts

src/mol-repr/volume/direct-volume.ts

src/mol-repr/volume/isosurface-mesh.ts

src/mol-repr/volume/registry.ts

src/mol-repr/volume/representation.ts