support non-github plugins

[teto]

I wanted to add https://git.sr.ht/~whynothugo/lsp_lines.nvim to nurr but so far it showcases only github plugins.
I think I found only one case where we could not use a full url instead of the github handles USER/REPO in:
.github/workflows/publish.yml

     - name: Checkout plugin repository
       uses: actions/checkout@v4
       with:
         repository: ${{ matrix.plugin.name }}
         path: .
         fetch-depth: 0

https://github.com/actions/checkout

seems like repository could accept the sr.ht url too. Gonna try

[teto]

first try at #33