Outdated documentation link

[JoshOrndorff]

At the bottom of the left sidebar there is a link titled "Documentation" that points to docs.substrate.dev/docs

At minimum the url should be updated, but perhaps the anchor text should also be changed to something like "Substrate developer hub" or "More substrate docs"

[soc1c]

yeah, getting the same. some domain moved apparently.

[shawntabrizi]

fixed in #123