add R languagae server (sublimelsp#263)

https://github.com/REditorSupport/languageserver

Author: randy3k

LSP.sublime-settings

@@ -155,6 +155,20 @@
           "fixOnSave": false
         }
       }
+    },
+    "rls":
+    {
+      "command": ["R", "--quiet", "--slave", "-e", "languageserver::run()"],
+      "languageId": "r",
+      "scopes":
+      [
+        "source.r"
+      ],
+      "syntaxes":
+      [
+        "Packages/R/R.sublime-syntax",
+        "Packages/R-Box/syntax/R Extended.sublime-syntax"
+      ]
     }
   },