Enable PWM for illumination LEDs on LL2+ and LL3

[thatcomputerguy0101]

This enables PWM on pins 13 and 18 to control the built-in dimmable illumination LEDs on Limelight 2+ and 3. The symlink at /boot/config.txt exists since that is the only path diozero checks for pwm configuration right now, and should be removed once diozero is updated to check /boot/firmware/config.txt or another source of PWM information (diozero#230).

Both LL2+ and LL3 have non-flickery LED dimming with these changes.

Needed to fix flickering LEDs in photonvision#2335.

[thatcomputerguy0101]

Deploying this image on a LL2+ fixed the flickery LED issues of photonvision#2235

[thatcomputerguy0101]

I might be able to test a LL3 tomorrow.

[thatcomputerguy0101]

LL3 wasn't working with the LL2 config.txt, so I created a separate config.txt file for it.

[mcm001]

Missing changes to https://github.com/PhotonVision/photon-image-modifier/blob/main/.github/workflows/main.yml for limelight 3

[thatcomputerguy0101]

Missing changes to https://github.com/PhotonVision/photon-image-modifier/blob/main/.github/workflows/main.yml for limelight 3

What changes? I didn't add an install script, so I think everything there still works. The LL3 script is actually quite similar to the LL3g and LL4 scripts now.

[mcm001]

Oh you're so right. No changes to the workflow.

I'm curious why we have different limelight and LL3 scripts -- they seem largely similar? -- but that's a topic for later.

[thatcomputerguy0101]

The limelight script (and config.txt) probably need to be reworked, but I'm concerned about doing that mid-season.

[crschardt]

This will work until we can get the config file location upstreamed.