Add changelog for 0.40.0-rc3

CHANGELOG.md

+## 0.40.0-rc3 (2024-11-05)
+
+### Added (1 change)
+
+- [Pass `plan` input down from compound templates](https://gitlab.com/components/opentofu/-/commit/4005bfaa98b82c73fbadaff6428398f9a0af15d6) ([merge request](https://gitlab.com/components/opentofu/-/merge_requests/169))
+
+### Development (1 change)
+
+- [This is a changelog test commit](https://gitlab.com/components/opentofu/-/commit/7cba70e7b82843b05bf4c5bfcb2e7260596e4d04)
+
 ## 0.40.0-rc2 (2024-11-05)
 
 ### Added (1 change)