[WIP] Add LED footprints for MX

[Gigahawk]

Relates to #23

For now this is implemented as a completely different footprint that the user would overlay on top of the keyswitch footprint.
There's also the option to have the LEDs baked into the keyswitch footprint like it is in MX_Alps_Hybrid, although that will require a custom symbol containing LED and Switch together, not sure which approach is preferred, or both.

TODO:

• Add 3d models
• Add footprints for THT LEDs
• Add footprints for RGB THT LEDs? (does anyone use these?)
• Add footprints for SMD 6028 LEDs (RGB and monochrome)
  • I am unaware of any clean way of getting KiCad to place 3d models on the bottom of a board, more than likely this will require the footprint to be made with top pads (LED firing down), and then the user will have to flip them as part of layout

[Gigahawk]

Dimensions based on MX_Alps_Hybrid, I've had success with these dimensions in the past:
https://github.com/ai03-2725/MX_Alps_Hybrid/blob/master/MX_Only.pretty/MXOnly-1.25U.kicad_mod#L23-L24

[perigoso]

this is not really the approach I was looking to implement, to start with I would like to have the space available for leds labeled on the switch, this is an interesting idea, but with so much variation between switches, and the different leds available, i dont think its viable, we would have to generate a large amount of footprints, and it would be confusing

[Gigahawk]

this is not really the approach I was looking to implement, to start with I would like to have the space available for leds labeled on the switch, this is an interesting idea, but with so much variation between switches, and the different leds available, i dont think its viable, we would have to generate a large amount of footprints, and it would be confusing

Having the locations marked on a user layer in the actual switch footprint is an option, but imo it's not that great for actually making keyboards

• actually placing a separate footprint directly at the marker location will be hard unless the mouse snap grid is set right and the switches are on the same grid
• having LEDs show up correctly in the 3d export doesn't really work unless we make separate footprints with the LEDs elevated to the correct height anyways

As for the different types of LEDs, I'm not aware of any other type of LED that someone might want to put into/under a switch; the current ones I've proposed should be fairly straightforward, and even then it should be obvious what the outcome will look like if we have 3d models.

[perigoso]

I changed my mind on how I want this to work, I want to have the LEDs embedded in the footprint, behaving like the keycaps do right now in the scripts, they wont be included in the default library but will be generate-able now manually, and later through the TODO plugin
This comes with a couple problems to solve, the positioning needs to be handled somehow in the switch class, presumably after the Led class has been created
And the hardest I think is handling the Library symbols, perhaps for now we could have a couple fixed options, essentially one for each LED, but at some point automatic generation and assignment should be considered