Auto-close backticks

Typing a backtick now automatically adds a closing backtick as well.
Also possible to quickly add add backticks are ident by selecting and
typing backtick.

Fixes #279

Author: harpocrates

language-configuration.json

@@ -20,13 +20,15 @@
         ["s\"", "\""],
         ["f\"", "\""],
         ["raw\"", "\""],
+        ["`", "`"]
     ],
     // symbols that that can be used to surround a selection
     "surroundingPairs": [
         ["{", "}"],
         ["[", "]"],
         ["(", ")"],
         ["\"", "\""],
-        ["'", "'"]
+        ["'", "'"],
+        ["`", "`"]
     ]
 }