README: make use cases less loud

I am going to add some additional use cases so lets move to h4 instead
of an h2.

Signed-off-by: Brandon Philips <[email protected]>

Author: Brandon Philips

README.md

@@ -22,10 +22,11 @@ In the specifications in the above table of contents, the keywords "MUST", "MUST
 
 To provide context for users the following section gives example use cases for each part of the spec.
 
-## Filesystem Bundle & Configuration
+#### Filesystem Bundle & Configuration
 
 - A user can create a root filesystem and configuration, with low-level OS and host specific details, and launch it as a container under an Open Container runtime.
 
+
 # Releases
 
 There is a loose [Road Map](./ROADMAP.md).