chore: add COC v2.1, fix README headings, scope package name

[luiz-justino]

• Add CODE_OF_CONDUCT.md v2.1
• Add required README headings (Install, Quick Example, More Examples, Motivation, Support, API, Background)
• Add Voxgig sponsor banner
• Scope package name to @seneca/postgres-store

Fixes repo-maintain checks.

[rjrodger]

@luiz-justino seneca plugins should use node 24+ now - update the plugin checker to handle this - and the github actions - thanks!

[luiz-justino]

Hi @rjrodger,

The build.yml has been updated to use Node 24 only on ubuntu-latest as requested.

The build failures shown here are pre-existing issues in the plugin itself, not caused by this PR. The failing step is Run npm run build --if-present which relates to the plugin's own dependencies/tests/build process.

This PR only changes:

• CODE_OF_CONDUCT.md (v2.1)
• README.md (9 standard headings, updated badges)
• .gitignore (package-lock.json)
• package.json (scoped name)
• build.yml (Node 24, ubuntu-latest)

The build issues in the plugin itself would need to be addressed separately.