Point the repo homepage, README and NuGet pages at the docs site and the walkthrough #424

Problem

The documentation site (#417) and the walkthrough (#418) are live, but readers mostly arrive somewhere else first:

• The GitHub repo's homepage is a Hashnode article from June 2026 that describes a much earlier version. The repo description mentions ranges and multiranges only, and value sets have been half the library since v6.
• nuget.org shows the package READMEs, and none of the four mentions the site or the walkthrough. Its "Project website" link (PackageProjectUrl) points at the GitHub repo, which RepositoryUrl already covers.
• The README's badge row puts two June 2026 articles next to the status badges, where they read as current. The Quick start ends at Getting started, with no pointer to the walkthrough.

Change

• Repository settings: set the homepage to https://caffeinatedcoder.github.io/CodoMetis.ValueRanges/ (the root, which always sends readers to the default line), and add value sets to the description.
• README: a Docs badge first in the row. The two article badges move to a dated "Further reading" line. The Quick start points to the walkthrough next to Getting started.
• Package READMEs: one line each linking the site and the walkthrough, with absolute links.
• PackageProjectUrl: points to the docs site.
• Changelogs: a Docs: line in the root changelog and each package changelog.

The package changes reach nuget.org with the next published version. Cherry-pick into release/10.x for 10.3.0.

Done when

• The repo shows the new homepage and description.
• The packed .nuspec has the docs site as projectUrl, and each package README links the site and the walkthrough.
• The port to release/10.x is merged (close this issue by hand if it lands after the main PR).