File PACKAGING_README.md of Package synp

# Packaging synp

As there is no OBS service to vendor yarn dependencies, this package contains a
Makefile. To execute the vendoring, you need to have `make`, `yarn`,
`obs-service-tar_scm` and `obs-service-set_version` installed locally.

1. Change the version in the `_service` file
2. Run `make`
3. Check the autogenerated changelog entry
4. Commit the changes as usual