FR: Show [Obsolete] status and message in documentation view

[mindsolve]

This is an extension to the FR #167 to also display the [Obsolete] status and message in documentation view, not only in the diff.
I would like to be able to directly see whether an API is deprecated.

[mindsolve]

I have created a proof-of-concept in my fork, based on PR #171 (adding obsolete status to the diff view): https://github.com/mindsolve/FuGetGallery/tree/feature/173-obsolete-status-in-doc-view

I would appreciate feedback before opening the PR, especially with the design.

Feature status of POC:

• Obsoletion information for type members
  • Example: package MineStat, screenshots below
• Obsoletion information directly on types
  • Example: Newtonsoft.Json.Schema.Extensions, where the whole class is marked as obsolete
• Obsoletion information directly in Namespace overview
  • Example again: Newtonsoft.Json.Schema.Extensions, where the whole class is marked as obsolete

Screenshots:

• Example of member with documentation and obsoletion message:
  
• Same snippet in dark mode:
  
• Example of member without documentation and with empty [Obsolete] constructor
  

[jamesmcroft]

Merged your changes for this into the #171 PR 😄

[mindsolve]

Very nice, thank you @jamesmcroft! Do you think that the two open points (comment above) should also be added in that change? Or do we leave it like this, as it covers the most common uses and possibly add them later?