add demo page

Author: MuffinK

README.md

@@ -1,3 +1,16 @@
 # single-number-input-vue
 number input using single char
 
+## Example
+
+password mode
+
+![demo](pic1.png)
+
+number input mode
+
+![demo](pic2.png)
+
+demo page
+
+https://muffink.github.io/

index.html

@@ -13,12 +13,16 @@
     <single-number-input v-model="value" ch-number=6 >
     </single-number-input>
     result: {{value}}
+    <single-number-input v-model="value2" ch-number=6 password=true>
+    </single-number-input>
+    result: {{value2}}
   </div>
   <script>
     new Vue({
       el: "#app",
       data: {
-        'value': ''
+        'value': '',
+        'value2': ''
       },
       components: {
         'single-input-number': 'single-input-number'