Fix #223: changelog

changes/changelog.d/223.feature

+Files management interface for users with "library" permission (#223)
+
+Files management interface
+^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+This is the first bit of an ongoing work that will span several releases, to
+bring more powerful library management features to Funkwhale. This iteration
+includes a basic file management interface where users with the "library"
+permission can list and search available files, order them using
+various criterias (size, bitrate, duration...) and delete them.