Add demo links for both usages

README.md

@@ -37,6 +37,9 @@ This project is sponsored by <a target="_blank" href="https://www.cloudflare.com
 ## Usage
 
 ### With NPM and Gulp (Recommended)
+
+**Demo:** [https://qr.huangxin.org](https://qr.huangxin.org/)
+
 ```bash
 git clone https://github.com/qr-merger/merger
 cd merger
@@ -50,6 +53,8 @@ An optimised version will appear at `/build` directory. Works well with JAMStack
 
 ### Standalone
 
+**Demo:** [https://qr.huangxin.org/standalone](https://qr.huangxin.org/standalone.html)
+
 1. Download [merger.html](https://github.com/qr-merger/merger/blob/master/merger.html).
 2. Edit its contents.
 3. Serve the html file per your liking.