Add documentation for 'Share project with group' API call

CHANGELOG-EE

+v 8.1.0
+  - Add documentation for "Share project with group" API call 
+
 v 8.0.1
   - Correct gem dependency versions
   - Re-add the "Help Text" feature that was inadvertently removed

doc/api/projects.md

@@ -477,6 +477,20 @@ Revoking team membership for a user who is not currently a team member is consid
 Please note that the returned JSON currently differs slightly. Thus you should not
 rely on the returned JSON structure.
 
+### Share project with group
+
+Allow to share project with group.
+
+```
+POST /projects/:id/share
+```
+
+Parameters:
+
+- `id` (required) - The ID of a project
+- `group_id` (required) - The ID of a group
+- `group_access` (required) - Level of permissions for sharing
+
 ## Hooks
 
 Also called Project Hooks and Webhooks.