work on defining actions and keyboard mappings

[mithrendal]

some more work on managing actions and keyboard mappings is ready

• in the right upper corner we can list all defined actions or mappings. Left the optional button label and right the optional keyboard mapping.
• in the picture in total 5 actions or mappings are defined

action is triggered either by a button or a keyboard mapping or both

• one can now leave the button label empty in which case the action will be triggered by a keyboard mapping only. no action button is visible then. (In the picture I mapped on an apple keyboard command+M to toggle the menu bar.)

two new actions

• menubar which toggles the menubar
• clipboard_paste paste the content of the clipboard into the C64 keyboard buffer.

pushed to https://vc64web.github.io 😎