Base: Write some initial man pages

It ain't much, but it's honest work!

Base/usr/share/man/man1/mkdir.md

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+## Name
+
+mkdir - create a directory
+
+## Synopsis
+
+```**sh
+$ mkdir path
+```
+
+## Description
+
+Create a new empty directory at the given *path*.
+
+## Examples
+
+```sh
+$ mkdir /tmp/foo
+```