Valid tag names can include any digit [0-9] (#66)

Author: jlalmes

src/snapshot.ts

@@ -10,7 +10,7 @@ import {
 } from './types';
 
 let _id = 1;
-const tagNameRegex = RegExp('[^a-z1-6-_]');
+const tagNameRegex = RegExp('[^a-z0-9-_]');
 
 export const IGNORED_NODE = -2;