1. Dozens of document improvements. Thanks @BryanLa!
2. Bug fix:
   1. Show cref name instead of missing if not resolved. Thanks @Emdot! (#7245)
   2. Fix showing wrong syntax for nullable value types. Thanks @mikernet! (#7045, #5964)
   3. Fix exception when loading memberpage plugin. Thanks @jamiehankins! (#7422)
   4. Get latest Visual Studio version when creating MSBuild instance. Thanks @jamiehankins (#7463)