Add warnings summary to console output

[joshuadavidthomas]

Pytest builtin reporter

================================================= warnings summary =================================================
tests/test_rich.py::test_outcomes
tests/test_rich.py::test_outcomes
tests/test_rich.py::test_collect_error
tests/test_rich.py::test_collect_error
  /home/josh/projects/pytest-rich/src/pytest_rich/plugin.py:27: PytestDeprecationWarning: The hookimpl pytest_configure uses old-style configuration options (marks or attributes).
  Please use the pytest.hookimpl(trylast=True) decorator instead
   to configure the hooks.
   See https://docs.pytest.org/en/latest/deprecations.html#configuring-hook-specs-impls-using-markers
    @pytest.mark.trylast

-- Docs: https://docs.pytest.org/en/stable/how-to/capture-warnings.html

• Add support for built-in --disable-warnings/--disable-pytest-warnings command line option #63