This patch adds the alternate_shortcut member to LibGUI::Action, which
enables one Action to have two keyboard shortcuts.
Note that the string used in menus and tooltips only shows the main
shortcut, which is the same behaviour as in Firefox and Chrome.
This changes (context) menus across the system to conform to titlecase
capitalization and to not underline the same character twice (for
accessing actions with Alt).
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 *
Actions can now have a longer text description, in addition to its
regular UI string. The longer text will soon be used to display
a more detailed description of hovered actions in statusbars.
