WIKI: Support "home.md" for folders

Description

Now that there's folder support, there's no option to access the "folder" itself

Example Structre

home.md
folder/
folder/home.md
folder/page.md

home.md is the main page shown when I access the WIKI.

When I access folder/page.md I see this breadcrumb:

folder/page

But folder isn't clickable and it doesn't lead anywhere anyway.

Proposal

I suggest the wikis/folder URL will redirect to wikis/folder/home.md, and that the "folder" in the breadcrumb be clickable and lead there.

Links / references

Documentation blurb

Overview

What is it?

A suggestion to add a default page for folders.

Why should someone use this feature?

It helps navigate a tree structure wiki

What is the underlying (business) problem?

Huge WIKIs are hard to navigate

How do you use this feature?

Use cases

When you have a huge WIKI

Feature checklist

Make sure these are completed before closing the issue, with a link to the relevant commit.