Add YASnippet-related keywords to package manifest

Author: Alhadis

package.json

@@ -2,7 +2,7 @@
 	"name": "language-emacs-lisp",
 	"version": "1.2.0",
 	"description": "Emacs Lisp support for Atom.",
-	"keywords": ["Emacs", "Lisp", "Elisp", "Scheme", "GNU", "FSF"],
+	"keywords": ["Emacs", "Lisp", "Elisp", "Scheme", "GNU", "FSF", "YASnippet", "YAS"],
 	"repository": "https://github.com/Alhadis/language-emacs-lisp",
 	"license": "ISC",
 	"engines": {