feat(go/plugins/compat_oai): add `deepseek` plugin

[hugoaguirre]

Checklist (if applicable):

• [x] PR title is following https://www.conventionalcommits.org/en/v1.0.0/
• [x] Tested (manually, unit tested, etc.)
• [x] Docs updated (updated docs or a docs bug required)

[morigs]

Hi, I'm interested in Deepseek support in Genkit. What's the plan on this PR? Do you need some help?

[hugoaguirre]

Hey @morigs, thanks for the interest. I need to check something internally with the team before resuming my work here.

I'll keep you posted 🙂

[hugoaguirre]

Missing custom base url support, adding it

[ipfans]

Is it ready for release, or does it require further work?

[hugoaguirre]

Hi @ipfans, @morigs. This PR is ready, however, we are going to release a minor update with bug fixes this week before including this and several other features to Genkit Go 😃.