Added a supported-versions page to the releases site

Repo: Jumoo/releases

Added a /versions page showing the highest release per supported Umbraco major for each package (e.g. uSync v13.4, v17.3, v18.1), grouped by category into collapsible sections, EOL majors shown dimmed rather than hidden
Added eol.json — Umbraco major → EOL date, sourced from Umbraco's LTS/EOL page
fetch-releases.mjs now resolves each release's real Umbraco major from NuGet dependency data (direct Umbraco.Cms.* dependency, or one hop through another tracked package) instead of assuming a package's own version number matches Umbraco's — fixes packages like uSync.Hangfire that version independently
Duplicated the site nav into the page header (not just footer) so it doesn't get lost as pages grow