Add support/installation for Codex

[art-shen]

Codex is the second major agentic CLI out there after Claude Code. Would be awesome to natively support it as well.

[samuelfaj]

Please!!!

[VincentBurke]

+1 NEED THIS!

[dmpvost]

+1 !

[paulo-advent]

You can build a wrapper and add the the rules of codex to route to rtk.. its not perfect, but it can already work.

[Zacaria]

Would this be acceptable ? #377

[yinjun1991]

+1

[jerrywu001]

+1

[tokezooo]

+1 need this

[WildCake]

+1

[fly8848]

+1