[docs] [overview] create LLM section and add examples: Part 1

[angelinalg]

Why are these changes needed?

Surface LLM/Generative AI use cases.

Request from @pcmoritz:
Can somebody put LLMs / generative AI into a separate section here https://docs.ray.io/en/latest/ray-overview/use-cases.html and also link some of the examples and latest blog posts? At the moment it is mixed together with Large Scale Workload Orchestration

Checks

• I've signed off every commit(by using the -s flag, i.e., git commit -s) in this PR.
• I've run scripts/format.sh to lint the changes in this PR.
• I've included any doc changes needed for https://docs.ray.io/en/master/.
  • I've added any new APIs to the API Reference. For example, if I added a
    method in Tune, I've added it in doc/source/tune/api/ under the
    corresponding .rst file.
• I've made sure the tests are passing. Note that there might be a few flaky tests, see the recent failures at https://flakey-tests.ray.io/
• Testing Strategy
  • Unit tests
  • Release tests
  • This PR is not tested :(

[angelinalg]

@pcmoritz Would you check that I pulled the correct items from the Large Scale Workload Orchestration section please? And I put LLM in the first position. Is that too bold?

I also just added the minimum to the intro sentence for LLM/Gen AI. I can ask @emmyscode for a better intro in a follow up PR.

[pcmoritz]

This is great, let's merge it! As a follow up if we have time we can add an intro and possibly a graphic if it is worth the effort. If you plan to do those let me know when it is ready for cherry-picking into the 2.4 branch :)

[zhe-thoughts]

@jjyao Do you think it's too late to pick into 2.4.0? Thanks

[jjyao]

No, we can still cherry pick.

[zhe-thoughts]

OK then I approve for picking