Add antlion as known_local_folder to pyproject.toml isort configuration

Change-Id: Ide790fde5403d1c1873e5f1db443a17013fae3da
Reviewed-on: https://fuchsia-review.googlesource.com/c/antlion/+/865457
Reviewed-by: Sam Balana <sbalana@google.com>
Commit-Queue: Patrick Lu <patricklu@google.com>
diff --git a/pyproject.toml b/pyproject.toml
index 4d6b1f9..1cf1b5d 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -62,6 +62,7 @@
 
 [tool.isort]
 profile = "black"
+known_local_folder = ["antlion"]
 
 [tool.mypy]
 mypy_path = "stubs"