Adding comment for typescript (zyedidia#3857)

Author: Neko-Box-Coder

runtime/plugins/comment/comment.lua

@@ -55,6 +55,7 @@ ft["swift"] = "// %s"
 ft["tex"] = "% %s"
 ft["toml"] = "# %s"
 ft["twig"] = "{# %s #}"
+ft["typescript"] = "// %s"
 ft["v"] = "// %s"
 ft["xml"] = "<!-- %s -->"
 ft["yaml"] = "# %s"