Add Multiple key support back in EMUK (or reviving the HOLD)

[jupiterbjy]

Suggestion

Either of this suggestions would make my duckypad usable again, or I might need to downgrade firmware (hope it works!)

1. Add back HOLD's 2 (or more the better) key support in EMUK

   • Might break compatibility?

2. Allow use of multiple EMUK lines in single button

3. Revive deleted HOLD

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Encountering issue

I was delaying update of firmware and just recently updated, and found out HOLD SHIFT SPACE is now EMUK SHIFT SPACE and syntax is no longer valid.

Previously HOLD command could held up to 2 keys:

duckyPad/duckyscript_info.md

Line 352 in a2531bf

`HOLD` command can be followed by up to 2 keys, they can be character or special keys.

Now, since EMUK don't support this and even worse there can't be 2 EMUK in a button, I have no way of setting Shift + Space hold down hotkey for arbitrary canvas rotation action, which looks like this:

One could edit the hotkey in software they use but there's some softwares that does not allow this - and it doesn't sounds right to rely on AutoHotkey to reassign it just to make it reassigned on duckypad.

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Attempted workaround

Since now Variables are added, I tried using variable & loop:

KEYDOWN SHIFT
KEYDOWN SPACE

WHILE $_READKEY != 0
    DELAY 50
END_WHILE

KEYUP SHIFT
KEYUP SPACE

Which actually does not work, as issue indicated on #144 I can't maintain the loop.