docs(external): add missing Quad9 credits in previous releases

[esensar]

Summary

This adds missing Quad9 credits in my PRs from previous releases, because that work was sponsored by Quad9.

Change Type

• Bug fix
• New feature
• Non-functional (chore, refactoring, docs)
• Performance

Is this a breaking change?

• Yes
• No

Does this PR include user facing changes?

• Yes. Please add a changelog fragment based on our guidelines.
• No. A maintainer will apply the "no-changelog" label to this PR.

Checklist

• Please read our Vector contributor resources.
  • make check-all is a good command to run locally. This check is
    defined here. Some of these
    checks might not be relevant to your PR. For Rust changes, at the very least you should run:
    • cargo fmt --all
    • cargo clippy --workspace --all-targets -- -D warnings
    • cargo nextest run --workspace (alternatively, you can run cargo test --all)
• If this PR introduces changes Vector dependencies (modifies Cargo.lock), please
  run dd-rust-license-tool write to regenerate the license inventory and commit the changes (if any). More details here.

---

Sponsored by Quad9

[esensar]

Is this an alright way to credit sponsorship in releases? I can see that multiple contributors are supported in changelog entries and release notes, so I figured that would be the best place to credit Quad9.

[pront]

Hi @esensar, did you check how this renders? Otherwise, LGTM

[esensar]

Hi @esensar, did you check how this renders? Otherwise, LGTM

Yes, it looked alright, just listed both my name and Quad9 (with GH link) alongside each other.