Support template arguments in rustdoc

[codehearts]

This can be done with the template file, but would it make sense for the rustdoc to also support template arguments? I currently have a rustdoc where the non-template output has been perfect, but I'd like to populate the version in the install instructions without creating a separate template file

I can understand if this is infeasible because the rustdoc is used elsewhere (crates.io?) where the template arguments wouldn't be parsed, so I guess this is more of a question than a request