feat: Add comport external for serial communication

[madskjeldgaard]

This pull request adds the comport external to allow for serial communication when in plugin mode. Fixes #2268

[timothyschoen]

Hi! It's probably better to send this PR to the ELSE library. We generally don't add single objects to plugdata, instead every object in plugdata should come from either ELSE, Cyclone or Gem.

This is for a few reasons:

• It makes it easy to use plugdata patches in pure-data, simply by installing those 3 libraries. The more separate objects we add, the more difficult this becomes
• Shifts the maintenance burden to other developers (mostly @porres), so that I can spend my time on plugdata itself, instead of also having to maintain separate objects going into the future.
• Adding it to ELSE will make sure the helpfile and object design will be consistent with the other objects included with plugdata. Also: If porres decides to add a comport object to ELSE, we'd either have 2 comport objects, or we'd be forced to remove one and break backward compatibility

[madskjeldgaard]

Okay, fair enough. I'll make a PR at Else :)

…

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[dromer]

It would be a bit odd to fork comport object over this though.

I do think that it's the most relevant object and behavior that people would expect.

But yeah I understand not wanting to have to deal with a plethora of upstream project to integrate and sync to plugdata.

[timothyschoen]

It would be a bit odd to fork comport object over this though.

I get that too, but since the goal of ELSE is to create a library that gives pure-data a "batteries included" type experience similar to what Max offers, I think including a comport object in ELSE does make a lot of sense.