fix(core): change with_command type to include list of strings (testcontainers#789)

the `with_command` function can actually take an argument with type
`list[str]`.

Co-authored-by: amirhosein <amirhosein@cyberdesign.se>

Author: AmirHosein-Gharaati

core/testcontainers/core/container.py

@@ -155,7 +155,7 @@ def get_exposed_port(self, port: int) -> int:
             return self.get_docker_client().port(self._container.id, port)
         return port
 
-    def with_command(self, command: str) -> Self:
+    def with_command(self, command: Union[str, list[str]]) -> Self:
         self._command = command
         return self