Handle name collisions with special wiki page names (Home, _Sidebar, _Footer)

[mattt]

If a public type is named Home, _Sidebar, or _Footer, its generated documentation would be overwritten by the special page of the same name. We should add logic in the generate subcommand to handle this possibility.

[mattt]

Since this is unlikely to happen and it's unclear what the correct should be, the best course of action would be to log a warning.