libs/unit: Add command index search to ASR unit.

Signed-off-by: tinyu <[email protected]>

Author: TinyuZhao

m5stack/libs/unit/asr.py

@@ -287,6 +287,9 @@ def search_command_num(self, command_word: str) -> int:
 
                 asr.search_command_num("custom command")
         """
+        for key, value in self._COMMAND_LIST.items():
+            if value[0] == command_word:
+                return key
         return -1
 
     def search_command_word(self, command_num: int) -> str: