Updated shortcut controls based on https://github.com/lewish/asciiflow/pull/212

[lewish]

Branched from https://github.com/lewish/asciiflow/pull/212

• Changes rendering / layout
• Hides shortcut buttons until alt is pressed
• Adds help text for shortcuts
• Prevents default alt + number behaviour on chrome that switches tabs

[lewish]

@ade-sede FYI!

[lewish]

Looks like this when alt is pressed:

Looks like normal otherwise:

[ade-sede]

This looks very good !