Fix garnix errors

- Remove non-derivations from packages
- Disable devshell evaluation in CI
diff --git a/garnix.yaml b/garnix.yaml
new file mode 100644
index 0000000..c86698d
--- /dev/null
+++ b/garnix.yaml
@@ -0,0 +1,3 @@
+builds:
+  exclude:
+  - devShells.x86_64-linux.default