Take into account html_copy_source option

[jbms]

Currently, "edit" and "view source" links are handled via the upstream mkdocs-material content.action.{edit,view} features, which always just link to github or other source repo.

But that means the source files copied via html_copy_source (which defaults to true) are never referenced.

Not clear what the default should be, but we should ensure that the source files are copied if, and only if, they are actually going to be referenced.

[2bndy5]

IMO, the current behavior is as expected per upstream behavior.

In other sphinx themes, I seldomly find it helpful to see the doc source. It may be useful to see the generated code output, but that isn't often useful to consumers (not the docs' authors).

On the other hand, the viewsource sphinx ext does link to the copied sources. This is often more useful than some mkdocs plugins which target the source code checked into the remote (which may not be the same as the version used to build the docs).