Add details about existing nano-COM compiler library and include desc…

…ription of features and code snippet usage (#197)

* Work in progress (describing existing interface design/features)

* Add more content about types and helper library

* Add information about DXIL container inspection/manipulation support

* Add PDB utilty interface information

* Add skeleton section for How To snippets on using the DXC library

* Update titles/links

* Fix code snippet comment

* Add snippet on how to compile a shader

* Get ID3D12ShaderReflection from output

* Added more code snippets

* PR feedback and added ID3D12ShaderReflection info

* Removed excessive links and added ID3D12ShaderReflection link

* Add optimizer call snippet

* Separated api descriptions/code snippets into its own section

* PR feedback