Implement modifiers in the from side.
This commit makes two modifiers as a key possible (#69). The expression grammar becomes 'ModKeyA:ModKeyB=Key[|OtherKey][;NextExpression]'. ModKeyB being pressed along will only be remapped if ModKeyA is being pressed. Leaving out ModKeyA behaves like the old xcape.
Examples, 'Alt_L:Control_L=equal;Control_L:Alt_L=grave;Control_L=Escape'
Be aware the output equal and grave will become Alt_L + equal and
Control_L + grave.
What are you using this for? I feel that very few users needs this. If it should be added it should be fixed so that it only outputs the Key and not ModKeyA+Key. The documentation would need to be updated also.
I'm using left alt and right alt to do joystick motions for switching windows. I think the current outputs are fine since a user probably needs to remap the outputs.