detect and enable links in descriptions

[wamserma]

Some options refer to upstream documentation for more details. Such links should be clickable in the rendered view:

For example:

1. open https://mipmip.github.io/home-manager-option-search/
2. search programs.powerline-go.modules
3. https://github.com/justjanne/powerline-go should be rendered as a working link (as in this issue)

[mipmip]

working now.