Add Review Copy plugin 2.2.1 (generic/reviewCopy)

[fpodschwadek]

Adds a new <plugin> entry for the OJS Review Copy Plugin — a generic plugin that creates standardised, reviewer-ready copies of submission documents by POSTing each relevant file to a configurable external converter service and storing the returned file as a review copy on the submission. Supports optional bearer-token authentication against the converter and is safe for multi-journal OJS installations.

• Plugin repo: https://github.com/fpodschwadek/ojs-review-copy-plugin
• Release: 2.2.1
• OJS compatibility: 3.5.0.4
• Licence: EUPL v1.2

Pre-flight checks (self-verified locally)

• plugins.xml validates against plugins.xsd.
• Package URL returns HTTP 200 and the tarball's root directory
  is reviewCopy/ (matching the OJS-required layout).
• MD5 of the downloaded tarball matches the value declared in
  <release md5="97da868548ba4af1a90e7e3ad609a783">.