package.json: align description and keywords with the repo metadata

The npm description drifted from the GitHub one. Both now carry the same
line, with the benefit up front instead of the "no browser, no Python"
negation. Adds rgbw, nodejs, and led-art to keywords to match the repo
topics.

Also ships NOTICE in the tarball. The license split moved the
third-party notices out of LICENSE, and `files` only listed LICENSE, so
the published package would have dropped them.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01PZnUXRsLLnt2A7pR3X4Luj