edit URI changed from MkDocs

[garfieldnate]

MkDocs uses edit/master as the default edit_uri value, so without documentation stating otherwise I expected this to be the same in Portray, particularly because the documentation on edit_uri points to the documentation in MkDocs. Unifying this value with MkDocs would break clients, but it would be helpful to just let the user know that this is happening. A single-line message like, "edit_uri not set by user, defaulting to edit/main" (or edit/default) would be helpful.

[robbintt]

This is configurable. I tested it just now, as I had the same problem with an old repo:

E.g. in PyProject.toml:

[tool.portray.mkdocs]
edit_uri = "edit/master"