chore: migration of website repository - #2606

The website history was merged under website/ (see the preceding merge
commit). This commit adapts it to live inside the monorepo:

- website: add an env-gated webpack alias (JSONFORMS_LOCAL=true) so the
  site can render against the monorepo's locally built @jsonforms/*
  packages; add start:local / build:local scripts. Default builds still
  use the published versions, so CI and production are unaffected.
- ci: add .github/workflows/website.yaml to build the site on website/**
  changes (verify only, never deploy); exclude website/** from the
  library CI matrix.
- publish: trigger a Netlify build hook on stable releases only, so the
  site is published against the latest stable release and never on
  regular pushes (no rolling website).
- netlify: move config to the repo root with base=website and an ignore
  rule scoping deploy previews to website/ changes.
- copy-docs.sh: default the source repo to the monorepo root.
- move the daily console-error check workflow to the repo root and
  refresh its stale action versions.

Standalone, manually-triggered workflow that pins the website's
@jsonforms/* dependencies to a given stable release, verifies the site
builds, pushes the bump, and triggers the Netlify deploy. Kept separate
from publish.yaml so a website failure never blocks a published npm
release and the site stays independently redeployable.

The optional regenerate_docs input rebuilds the typedoc API docs from
the current state of master (no tag checkout) and commits the refreshed
website/static/api together with the pin, replacing the manual
copy-docs step. Run it right after a stable release, while master still
matches the released code.

Drop the deploy-hook trigger from publish.yaml in favor of this
workflow: it fired before the website's dependencies were bumped, so it
deployed the site against the previous release. release-website is now
the single deploy path; netlify.toml's comment points at it.