Improve docs

[waitxd]

• Link to Hints to achieve maximum performance when using MessagePack for C# in table of content is now working.
• Fixed typos like ReadOnlyOnservableCollection, obejct, protbuf-net, protonet-buf, etc.
• Used MessagePack instead of msgpack and messagepack. It's official name of format.
• Used Json.NET instead of JSON.NET. It's official name of package. However, JSON is still uppercase.
• Fixed CompositeResolver creation example since it is static now.

[AArnott]

Awesome. Thanks!