Remove wxLC_SINGLE_SEL flag from the file list control in the Git Commit
dialog to allow users to select multiple rows. When a checkbox is toggled
for an item that is part of a multi-selection, all selected items are
toggled together, making it easier to batch check/uncheck files.
Fixes https://gitlab.com/kicad/code/kicad/-/issues/15910
Recommendation is to avoid using the year nomenclature as this
information is already encoded in the git repo. Avoids needing to
repeatly update.
Also updates AUTHORS.txt from current repo with contributor names
Seth Hillbrand