jsdom relies on Node.js-specific APIs that Bun cannot properly resolve
when running a bundled artifact. This caused an EISDIR error in Docker
containers (Bun tried to read the jsdom directory as a file).
Replace jsdom with linkedom, a lightweight pure-JS DOM implementation
that is fully compatible with Bun and @mozilla/readability. Also remove
the --external jsdom build flag since linkedom bundles cleanly.
Closes#181
Acbox