Add secondaryKey option for 2d navigation

[marwahaha]

fixes #290

For example, my use case is

node decktape.js  --key=ArrowDown automatic 'https://hackmd.io/@kmarw/SJxRLR3DO2?controls=false&fragments=false' ~/test.pdf

There is a bug however; the first slide seems to print twice. Why is this? This happens:

• on this branch, when I use a secondary key or not.
• on the latest release, when the key does not advance the slides.

It does not happen

• on the latest release, when the key advances the slides.
• on my previous branch https://github.com/astefanutti/decktape/pull/289

My guess is that it happens when the first key is pressed, and nothing has changed, but perhaps the page is still loading, so isNextSlideDetected is set to true. Just a hypothesis though. (For example, on my slide deck, the first slide advances with the secondaryKey, i.e. the key doesn't advance the slide.)

[marwahaha]

Thanks for the PR. I’m thinking this could be generalized by turning the key option into an array, instead of introducing an ad-hoc ˋsecondary-key` option.

I think this is not that easy; I tried to do this but nomnom's list: true option setting is only parsed when using generic command and not automatic.

[marwahaha]

This seems sort of complicated, and still doesn't fix the bug. Maybe it makes sense to allow the Hackmd plugin on its own.

[astefanutti]

@marwahaha I've created #292, that allows to run:

$ decktape generic 'https://hackmd.io/@kmarw/SJxRLR3DO2?controls=false&fragments=false' test.pdf --key ArrowDown --key ArrowRight

Which produces the following PDF document: test.pdf

[marwahaha]

I think this almost works, but has the same bug I mention (first slide is repeated twice).

[astefanutti]

I've fixed the duplicated first slides issue with 0b69015c99add781ee61519b32f9639c1d1866b7.

I get the following PDF document: test.pdf

Let me know if that works for you.

[marwahaha]

superseded by #292