Relicense photon-serde as MIT

[gerth2]

serde (currently GPLv3) is generating source files which are distributed with photon-lib (intended to be MIT). This is technically incompatible, as it implies photon-lib is actually GPLv3, not MIT as intended.

While we don't expect any individual FRC team to hit the threshold of distributing their software that uses photon-lib, we'd like to be technically correct anyway.

Change serde's licensing to be MIT (new license.txt file, new headers) to keep photon-lib entirely MIT.

As of commit e40c8fbca08e8397e00e35f72809ac69d752ad57 on main, contributors are:

 git shortlog -n -s -- photon-serde
     4  Lucien Morey
     3  Matt
     1  Jade

@LucienMorey @mcm001 @spacey-sooty before this proceeds, can you comment below with an explicit "agree" below that code you wrote will be relicensed from GPLv3 to MIT ?

[mcm001]

Yes, I'm happy to release my contributions to photon-serde and the autocode it generates under MIT.

I think we will still need to relicense photon-targeting right?

[spacey-sooty]

I am also happy with any of my contributions to photon-serde to be MIT.

[LucienMorey]

I agree

[auscompgeek]

I can split out the photon-serde change from #1702 if you'd like.