v1.2.1 — Rosa3D catalogue example, TigerSystem, refreshed reference data

Changed

• The catalogue example in the README, the docstrings and the playground is now product
  2673739332, Rosa3D PLA Rainbow - Fire 1000 g: 3527039449 (Elegoo Rapid TPU 95A - Black)
  left the catalogue. The tests that read the bundled copy use it too.
• The copyright and trademark holder is named TigerSystem (formerly TigerTag Corp) in the
  licence, the source headers and the README.
• Bundled reference data (database/) refreshed from the TigerTag API.

Added

• Showcase site (site/), published on GitHub Pages at
  https://tigertag-project.github.io/TigerTag-SDK-JS/ by .github/workflows/pages.yml:
  one static page per language (en, fr, de, es, it, zh, pt, pt-pt, pl, ru, nl) built by
  site/build.py from site/template.html and site/i18n/<lang>.json, with the install
  command, the README quick start, the features, the CLI and Electron samples, the
  playground, the ecosystem and an FAQ. The version, release date and code samples are
  read from package.json, this changelog and the README. site/seo_check.py checks
  every page (rule: .agents/rules/seo-geo.md). Not part of the npm package.
• README: a "Get started with the JavaScript SDK" button (assets/site-button.svg) and
  the site's language links at the top.