Update readme

Author: ManuelHentschel

configuration.md

@@ -62,6 +62,8 @@ The remaining config entries are:
 * `"workingDirectory"`: An absolute path to the desired work directory.
 Defaults to the workspace folder.
 The R process is launched in this directory (reading the `.Rprofile` there).
+* `"rPath"`: Path to the R executable.
+If not specified, the extension setting `r.rpath.XXX` is used.
 * `"file"`: Required for debug modes `"file"` and `"function"`. The file to be debugged/sourced before calling the main function.
 * `"mainFunction"`: Only used for debug mode `"function"`.
 The name of the main function to be debugged. Must be callable without arguments.