Shows how to implement the next/previous line behaviors for cursors.

Note that this is untested.

commit 6b11f21
Author: Chad Brokaw <cbrokaw@gmail.com>
Date:   Fri Aug 16 12:31:34 2024 -0400

    selection and editing

commit 951fc96
Author: Chad Brokaw <cbrokaw@gmail.com>
Date:   Fri Aug 16 10:13:13 2024 -0400

    checkpoint

commit ecd232d
Author: Chad Brokaw <cbrokaw@gmail.com>
Date:   Thu Aug 15 21:30:27 2024 -0400

    checkpoint

- support ctrl+home/end
- fix delete with non-collapsed selections
- move to start/end of line when maxing out up/down respectively
- fix panic on empty text buffer
- proper cursor placement when using left/right to collapse selection
- fix weird cursor offset bug when line ends with RTL run containing only whitespace that is reordered
- triple click to select line