Allow the user to highlight sections of the edited document, giving them
arbitrary background colors. These annotations can be created from a
selection, or by manually specifying the start and end offsets.
Annotations can be edited or deleted by right-clicking them.
Any color can be used for the background. Dark colors automatically make
the text white for easier readability. When creating a new annotation,
we use whatever color the user last picked as this is slightly more
likely to be the one they want.
Icons contributed by Cubic Love.
Co-authored-by: Cubic Love <7754483+cubiclove@users.noreply.github.com>
