add check_aliases command

e621.py

@@ -178,3 +178,7 @@ class E621:
         if 'success' in r:
             return []
         return [E621PostVersion.from_dict(p) for p in r]
+
+    async def get_tag_aliases(self, name: str) -> List[str]:
+        r = (await self.client.get('/tag_aliases.json', params={'search[antecedent_name]': name})).json()
+        return [alias['consequent_name'] for alias in r]