Add R starter workflow

This adds a workflow for [R packages](https://www.r-project.org/). It
uses a [setup-r](https://github.com/r-lib/actions/tree/master/setup-r) action and two R packages
  - [remotes](https://remotes.r-lib.org/) - to install the R package dependencies
  - [rcmdcheck](https://github.com/r-lib/rcmdcheck) - to run and format the output of the package checking tool used in the R ecosystem.

ci/properties/r.properties.json

@@ -0,0 +1,6 @@
+{
+    "name": "R package",
+    "description": "Create and test an R package on multiple R versions.",
+    "iconName": "R",
+    "categories": ["R"]
+}