Fix typos.

[waywardmonkeys]

Objective

To have fewer typos.

Context

This was largely done with the typos-cli tool to lay the ground work for being able to use it in CI potentially.

Feedback Wanted

One thing that makes this seem bigger is that it includes renaming files that had typos in their file names.

Also, I'm not sure where the original files are for the generated ones so that we can fix whatever was generating them if needed.

Finally, it is worth paying attention to the change in test_fixtures/flex/align_flex_start_with_stretching_children.html ...