Wiki would benefit from update for stack 1.9

[dbaynard]

In stack 1.9, template handling has changed to introduce namespaces (though this repo remains the default for non-namespaced templates).

Note: there's currently an issue commercialhaskell/stack#4394 which means github repos must be prefixed with github: on Windows.

[dbaynard]

I've added some details — but it is still fairly sparse.

[mpilgrem]

I have done another pass of the Wiki (for the position in 2022) and will close this issue.