[96pt] C++ connector: create Getting Started documentation [sprint #19]

[veod32]

Create the Getting Started document for Tarantool C++ connector (https://github.com/tarantool/tntcxx/).
Content source will be stored in the connector repository which should be added as a submodule to tarantool/doc.
In the final documentation view, this chapter should appear in https://www.tarantool.io/en/doc/latest/getting_started/.

Development issue: tarantool/tarantool#4877