[lldb][docs] add command to save core file in gdb to lldb command map. (#140771)

Author: da-viper

lldb/docs/use/map.rst

@@ -1350,6 +1350,17 @@ Dump all symbols in ``a.out`` and ``liba.so``
 
   (lldb) image dump symtab a.out liba.so
 
+Save current process as a core file
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+.. code-block:: shell
+
+  (gdb) gcore filename
+
+.. code-block:: shell
+
+  (lldb) process save-core filename
+
 Miscellaneous
 -------------