Add separator between OSMF preface and main docs

Author: kzu

src/ThisAssembly.AssemblyInfo/readme.md

@@ -1,4 +1,5 @@
 <!-- include https://github.com/devlooped/.github/raw/main/osmf.md -->
+## Overview
 <!-- #assembly -->
 This package generates a static `ThisAssembly.Info` class with public 
 constants exposing the following attribute values generated by default for SDK style projects:

src/ThisAssembly.Constants/readme.md

@@ -1,4 +1,5 @@
 <!-- include https://github.com/devlooped/.github/raw/main/osmf.md -->
+## Overview
 <!-- #constants -->
 This package generates a static `ThisAssembly.Constants` class with public
 constants for `@(Constant)` MSBuild items in the project.

src/ThisAssembly.Git/readme.md

@@ -1,4 +1,5 @@
 <!-- include https://github.com/devlooped/.github/raw/main/osmf.md -->
+## Overview
 <!-- #git -->
 This package generates a static `ThisAssembly.Git` class with constants 
 for the following Git properties from the current project:

src/ThisAssembly.Metadata/readme.md

@@ -1,4 +1,5 @@
 <!-- include https://github.com/devlooped/.github/raw/main/osmf.md -->
+## Overview
 <!-- #metadata -->
 This package provides a static `ThisAssembly.Metadata` class with public 
 constants exposing each `[System.Reflection.AssemblyMetadata(..)]` defined in 

src/ThisAssembly.Project/readme.md

@@ -1,4 +1,5 @@
 <!-- include https://github.com/devlooped/.github/raw/main/osmf.md -->
+## Overview
 <!-- #project -->
 This package generates a static `ThisAssembly.Project` class with public 
 constants exposing project properties that have been opted into this mechanism by adding 

src/ThisAssembly.Resources/readme.md

@@ -1,4 +1,5 @@
 <!-- include https://github.com/devlooped/.github/raw/main/osmf.md -->
+## Overview
 <!-- #resources -->
 
 This package generates a static `ThisAssembly.Resources` class with public 

src/ThisAssembly.Strings/readme.md

@@ -1,4 +1,5 @@
 <!-- include https://github.com/devlooped/.github/raw/main/osmf.md -->
+## Overview
 <!-- #strings -->
 
 This package generates a static `ThisAssembly.Strings` class with public 

src/ThisAssembly.Vsix/readme.md

@@ -1,4 +1,5 @@
 <!-- include https://github.com/devlooped/.github/raw/main/osmf.md -->
+## Overview
 <!-- #vsix -->
 Allows consuming VSIX manifest properties from code, as well as 
 MSBuild project properties from the VSIX manifest. For example:

src/ThisAssembly/readme.md

@@ -1,4 +1,5 @@
 <!-- include https://github.com/devlooped/.github/raw/main/osmf.md -->
+## Overview
 <!-- include ../../readme.md#meta -->
 
 ## ThisAssembly.AssemblyInfo