[FEAT] Caching, Gallery, and Multithreading

The PR rolls together a few of the previous PRs:

It adds automatic caching to all of the standard library functions, so incremental changes to complex models will regenerate much more quickly.
It begins to add a gallery frontend for users to post and share projects (though this is non-functioning at the time of writing).
It moves all of the CAD operations and heavy lifting work to a WebWorker thread (which has the benefit of unlocking the main thread during heavy recomputes AND sandboxing the execution of the scripts (making it safer to add shared authenticated community stuff to the main page)). Asynchronous Model Evaluation Progress is currently visualized by the number of ellipses after Generating Model....
It adds several new functions including the Offset() function and a Sketching interface for drawing arbitrary filleted 2D objects. Also utility functions for saving arbitrary files and extracting solids and wires.
Adds multi-font text rendering
Fixes a plurality of bugs around the expected inputs/outputs of various operations/functions.
Refactors Shape/Edge rendering to be in one draw-call, so large models (like loaded .stl's) will render MUCH more quickly! (even on mobile devices!)
Cleans up the directory structure and adds comments everywhere!

We'll get there very, very soon...

zalo / CascadeStudio