Previously move_selection() did not work as expected. Instead store the
selected layer index in a member variable and continue to cycle through
the layers when you come to the start/end. Also use it to scroll into
view. Lastly rename the function to cycle_through_selection() to make it
clearer what it does.
This enables the layer menu as a context menu in LayerListWidget,
setting the clicked layer as active for now, but in the future it
would be nice to have custom menu applying to the clicked layer instead
of the active layer.
SPDX License Identifiers are a more compact / standardized
way of representing file license information.
See: https://spdx.dev/resources/use/#identifiers
This was done with the `ambr` search and replace tool.
ambr --no-parent-ignore --key-from-file --rep-from-file key.txt rep.txt *
