docs(vrl): update documentation for parse_nginx_log with the main log format

[virtualtam]

Summary

This PR updates the documentation for the parse_nginx_log VRL remap function with an example for parsing a log line formatted using the main format (see VRL issue and PR referenced below for more information).

Change Type

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

Is this a breaking change?

• Yes
• No

How did you test this PR?

I have built the website documentation locally with:

$ cd rust-docs
$ make docs

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.
• 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.

References

• VRL issue: VRL: add main log format for parse_nginx_log vrl#1201
• VRL PR: feat(stdlib): Add main log format to parse_nginx_log function vrl#1202

Notes for reviewers

• Looking at the VRL and Vector contributing guides, I am not sure whether this PR requires adding a changelog fragment; if so, please suggest the appropriate format for the changelog entry 📖

[virtualtam]

Thanks @pront for merging this PR and fixing the typos in the Cue files 👍

Though I followed the CONTRIBUTING / Running other checks, I didn't catch these issues locally, and the Github CI seems to require maintainer approvale before jobs are started.

Looking at one of the failed CI runs, these errors are caught in the Check Cue docs step by running make check-docs: https://github.com/vectordotdev/vector/actions/runs/12715110995/job/35446822563

Maybe this command could be added to the CONTRIBUTING guide in a section for documentation-related PRs, as well as any relevant command to check the documentation generation locally?