Feature: Mesh subdivision

[Luca3317]

Is your feature request related to a problem? Please describe.
There are animations that would benefit from mesh subdivision.
For example, a wiggle effect can be much more detailed which matters especially on large text. Colors can fade from the center to the extents of the mesh, or characters can be split into pieces.

Describe the solution you'd like
A simple way to subdivide the character meshes, either integrated into TMPAnimator or as a new component.
The mesh modification API would have to be reworked to support both the standard 4 vertex quad mesh and arbitrarily subdivided meshes.
It should be possible to treat a subdivided mesh as a simple quad implicitly, to keep the API simple and compatible with all existing animations.

Additional context
Major potential issue with that right now:

• Meshes are limited to 16 bit indexing / 65532 vertices. Subdividing a mesh so that it exceeds this limit means the mesh will have to be split into multiple smaller submeshes with TMP_SubMesh(UI). Im not sure how to add such submeshes, as the collection in TextmeshProUGUI is private and (after some quick scanning) there seems to be no public methods that allow you to modify this list without destroying the TMP_Text and creating a new one. If anyone reads this and knows how to accomplish this please let me know :D