basic text rendering: render-object, builder, shader

src/mol-geo/geometry/text/text-builder.ts

src/mol-geo/geometry/text/text.ts

src/mol-gl/render-object.ts

src/mol-gl/renderable/schema.ts

src/mol-gl/renderable/text.ts

src/mol-gl/renderer.ts

src/mol-gl/shader-code.ts

src/mol-gl/shader/chunks/common-vert-params.glsl

src/mol-gl/shader/text.frag

src/mol-gl/shader/text.vert

src/tests/browser/render-text.ts