add radian support for R (#212)

* add radian support for R

* Remove some typos

lua/iron/fts/r.lua

@@ -1,7 +1,28 @@
 local r = {}
 
 r.R = {
-  command = {"R"},
+    command = { "R" },
+}
+
+local extend = require("iron.util.tables").extend
+
+local format = function(open, close, cr)
+    return function(lines)
+        if #lines == 1 then
+            return { lines[1] .. cr }
+        else
+            local new = { open .. lines[1] }
+            for line = 2, #lines do
+                table.insert(new, lines[line])
+            end
+            return extend(new, close)
+        end
+    end
+end
+
+r.radian = {
+    command = { "radian" },
+    format = format("\27[200~", "\27[201~\13", "\13"),
 }
 
 return r