📖 [Docs]: Move documentation to MSX / Docs and reduce the README to a pointer (#383)

Moves the Process-PSModule documentation to the MSX / Docs site and
reduces this repository's README to a short pointer.

The full documentation — getting started, pipeline stages, usage,
configuration, repository structure, and principles — now lives at
<https://msxorg.github.io/docs/Frameworks/Process-PSModule/>, added to
MSX / Docs in MSXOrg/docs#39.

## Changed: README

- The README is now a brief description plus a link to the documentation
on MSX / Docs. Everything previously in the README now lives in the new
Frameworks → Process-PSModule section of the docs site.
- The two diagrams (`media/Process-PSModule.png` and
`media/pagesEnvironment.png`) are removed; they were referenced only by
the README and now live alongside the docs.

## Technical Details

- Pairs with MSXOrg/docs#39, which adds the Frameworks/Process-PSModule
section. Merge that PR first so the README link resolves once GitHub
Pages redeploys.
- Labelled `NoRelease`: the README is an important file, but this is a
documentation-only relocation and should not cut a new version.
- `DEPENDENCIES.md`, the workflows, and all other files are unchanged;
the docs link to them by absolute URL.

Author: MariusStorhaug