added orthographic camera & combined camera

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

src/apps/canvas/component/viewport.tsx

src/apps/canvas/index.ts

src/apps/canvas/structure-view.ts

src/mol-canvas3d/camera/base.ts

src/mol-canvas3d/camera/combined.ts

src/mol-canvas3d/camera/orthographic.ts

src/mol-canvas3d/camera/perspective.ts

src/mol-canvas3d/canvas3d.ts

src/mol-math/linear-algebra/3d/mat4.ts