Allow BufferSerializer to be used directly in game code

[billw2012]

Is your feature request related to a problem? Please describe.
I want to reuse the network serialization for saving object state for save game, however the BufferSerializer constructor is internal so I can't create my own instance of it.

Describe the solution you'd like
Make the BufferSerializer constructor public, as well as BufferSerializerWriter and BufferSerializerReader.

Describe alternatives you've considered
My solution so far is copying the classes mentioned above into my own code, so I can access them, but this obviously isn't ideal, particularly when I update to a newer version.
Another alternative would be to provide a static function (or functions) that will make me a BufferSerializer instance for writing or reading.

[NoelStephensUnity]

That was made public awhile back.

[keyserjaya]

BufferSerializerReader and BufferSerializerWriter still not public in version 1.14

[keyserjaya]

Nevermind, i can use this as alternative.
Thank you.