SPPO Implementation on Axolotl!

[kaykyr]

Hey guys! For who is interested, I recently submitted a pull request to implements SPPO on Axolotl trainer, you can fallow the pull request here: https://github.com/axolotl-ai-cloud/axolotl/pull/1735

Original SPPO implementation fork: https://github.com/kaykyr/axolotl

See examples/llama3/sppo-qlora-8b.yml config file to see how train SPPO.