docs: update projectinfo.rst with latest pyzstd and zstd comparisons

[rungeard]

• Update zstd section to reflect latest release (1.5.7.2, June 23 2025).
  Clarify that it only supports basic compression/decompression and does not
  provide CFFI, streaming, or dictionary support.

• Update pyzstd section to reflect latest release (0.17.0, May 10 2025).
  Document its support for both C and CFFI backends, PyPy compatibility,
  CPython 3.12+ sub-interpreters, streaming compression/decompression,
  dictionary use/training, and seekable file format.

• Clarify that python-zstandard remains the most feature-rich binding,
  highlighting advanced features such as multiple streaming interfaces,
  precomputed dictionaries (precompute_compress), advanced tuning parameters,
  zero-copy buffer protocol support, frame inspection, and robust error
  handling.