vim-patch:8.1.0225: mode() does not indicate using CTRL-O from Insert mode (#9644)

Problem:    Mode() does not indicate using CTRL-O from Insert mode.
Solution:   Add "niI", "niR" and "niV" to mode() result. (closes vim/vim#3000)
612cc3888b

src/nvim/state.c

@@ -162,6 +162,10 @@ char *get_mode(void)
       buf[1] = 'o';
       // to be able to detect force-linewise/blockwise/characterwise operations
       buf[2] = (char)motion_force;
+    } else if (restart_edit == 'I' || restart_edit == 'R'
+               || restart_edit == 'V') {
+      buf[1] = 'i';
+      buf[2] = (char)restart_edit;
     }
   }