chore: Add .editorconfig for SWF tests

Add a dedicated .editorconfig for SWF tests as most files shouldn't be
formatted.

Author: kjarosh

tests/tests/swfs/.editorconfig

@@ -0,0 +1,8 @@
+root = true
+
+# Format only the test configuration, other files constitute tests and can
+# or sometimes even have to be formatted differently.
+[test.toml]
+end_of_line = lf
+insert_final_newline = true
+trim_trailing_whitespace = true