point to rmap if this is deprecated

Can the maintainers of this repo put pointer links in the `README.md` to `rmap` package which appears to be a more recent package?  Some of the folks starting to plot spatial maps using JGCRI tools might get confused about which one to use.

`rmap` repo: https://github.com/JGCRI/rmap
`rmap` wiki: https://jgcri.github.io/rmap/