CI: run also on test.sh changes

CI: run also on test.sh changes

The CI only tests packages if a Makefile changed, e.g. containing a
version or release bump. This covers package related files as at least
the package release must change whenever a file was touched.

The `test.sh` file is a runtime test used to verify working packages
within OpenWrt containers. This file can independently change and will
never be included in the package ipk files, therefore trigger the CI on
its changes as well.

Signed-off-by: Paul Spooren <mail@aparcar.org>