add a gitignore mode

lib/ace/mode/gitignore.js

@@ -0,0 +1,19 @@
+
+define(function(require, exports, module) {
+"use strict";
+
+var oop = require("../lib/oop");
+var TextMode = require("./text").Mode;
+var GitignoreHighlightRules = require("./gitignore_highlight_rules").GitignoreHighlightRules;
+
+var Mode = function() {
+    this.HighlightRules = GitignoreHighlightRules;
+};
+oop.inherits(Mode, TextMode);
+
+(function() {
+    this.$id = "ace/mode/gitignore";
+}).call(Mode.prototype);
+
+exports.Mode = Mode;
+});