add firefox extension template

externs/webextension_polyfill/contextualidentities/ContextualIdentity.hx

@@ -0,0 +1,31 @@
+package webextension_polyfill.contextualidentities;
+
+/**
+	Represents information about a contextual identity.
+**/
+typedef ContextualIdentity = {
+	/**
+		The name of the contextual identity.
+	**/
+	var name : String;
+	/**
+		The icon name of the contextual identity.
+	**/
+	var icon : String;
+	/**
+		The icon url of the contextual identity.
+	**/
+	var iconUrl : String;
+	/**
+		The color name of the contextual identity.
+	**/
+	var color : String;
+	/**
+		The color hash of the contextual identity.
+	**/
+	var colorCode : String;
+	/**
+		The cookie store ID of the contextual identity.
+	**/
+	var cookieStoreId : String;
+};