Set EnableRemoteLinkPicker: true in CheckFileInfo response so
Collabora Online exposes its "Smart Picker" UI for link
insertion. Clicking it sends a UI_PickLink postMessage to the WOPI
host, which is expected to reply with Action_InsertLink carrying the
URL of the selected file. Follows the same pattern as the existing
EnableInsertRemoteImage / EnableInsertRemoteFile flags.
Signed-off-by: Pedro Pinto Silva <pedro.silva@collabora.com>