v0.3.4 — Maintenance release: store listing image and build-toolchain dependency patches

Maintenance release: store listing image and build-toolchain dependency patches.

• No on-device/plugin behavior changes in this release.

Changed

• The plugin's store listing image no longer points at the plugin template's
  placeholder, which rendered a GitHub repository card for an unrelated
  project. It now shows Decky Metadata's own Steam Community controller
  layouts screenshot.

Security

• Patched four high-severity advisories in transitive build dependencies
  (brace-expansion, fast-uri), plus postcss, via a lockfile-only update.
  All are devDependencies of the rollup/vitest toolchain and are never part of
  the packaged plugin, so no installed plugin was ever exposed.