Support Turtle

Currently we only support nquads format, but not Turtle. We should support it as well, at least for parsing.

Implementing it from scratch doesn't make sense, we can use the implementation from one of the existing projects, see #3.

Start by reading issue #3 to identify the existing project implementation referenced there, then inspect how this repository currently supports N-Quads parsing. Determine where Turtle parsing belongs and verify that Turtle input is accepted without changing existing N-Quads behavior. Done means the package can parse Turtle using the selected implementation.

Written by the indexing model from the issue text.