Synology Router

I wonder is there a package to install PI-Hole in a Synlogy Router?

I used to have Synology running on raspberry pi for year, then I migrated to docker on my Synology DS918+.

At this stage I'm not have the DS918+ running all the time so I was hopping they was a way to install on the router himself.

There is not, and we do not plan on supporting router installs. There are multiple threads on this topic if you want to read more.