Add Edit context menu item for EEschema graphic lines.

Fixes: lp:1779554
* https://bugs.launchpad.net/kicad/+bug/1779554

(cherry picked from commit 02b29ba)

eeschema/onrightclick.cpp

@@ -277,6 +277,8 @@ bool SCH_EDIT_FRAME::OnRightClick( const wxPoint& aPosition, wxMenu* PopMenu )
                 AddMenuItem( PopMenu, ID_POPUP_END_LINE, _( "End Drawing" ),
                              KiBitmap( checked_ok_xpm ) );
 
+            AddMenuItem( PopMenu, ID_SCH_EDIT_ITEM, _( "Edit..." ),
+                         KiBitmap( edit_xpm ) );
             AddMenuItem( PopMenu, ID_POPUP_SCH_DELETE, _( "Delete Drawing" ),
                          KiBitmap( delete_xpm ) );
             break;