Implementing Typography for Skia

[tushar5526]

Closes #373
Related to #371

[tushar5526]

Hey @ziyaointl

I have called the preload right there in the userspace.py because it seemed the easy way instead of putting it in the base.py and calling it somewhere in the sketch class.

Also preload does not affect frame_count or any other sketch settings in any way so I called it in the userspace.py as of now.

Let me know your thoughts, and you can review this PR. It is good to go.

I will do multiple PRs this time and use issue #371 to keep track of the implementing typography status, instead of a single PR with many changes.

[ziyaointl]

Great work! I really appreciate the effort that you took to split up large PRs into small ones. This makes reviewing so much easier :D

One nit: I think that adding preload is conceptually different enough from the other font functions that this PR could be split up further, but this is just for future reference - no need to split up this particular PR now.

[ziyaointl]

Instead of passing in a default size of 10, we should probably use the current font size.

[tushar5526]

Yes, fixed it.

[ziyaointl]

Thanks! Looks like the size parameter is being ignored by vispy's text_font, could you also do a quick fix for that as well?

[ziyaointl]

And yes, I think putting preload in userspace.py is very reasonable :)

[tushar5526]

I have updated the PR and added a test for typography

[ziyaointl]

Kudos for adding the tests!