identiconSvg tree shaking + node <14 compatibility

README.md

@@ -55,6 +55,7 @@ By default the color saturation and lightness are set to 50%. But you can change
 ```html
 <identicon-svg username="alienHead66" saturation="95" lightness="60">
 ```
+
 Play with [the demo](https://laurentpayot.github.io/minidenticons/) to find a combination of saturation and lightness that matches your website theme colors: light, dark, pastel or whatever :sunglasses:
 
 ![Minidenticons](minidenticons_light.png)
@@ -77,6 +78,8 @@ npm install minidenticons
 import { identicon } from 'minidenticons'
 ```
 
+The `identicon-svg` custom element should be tree-shaken from your bundle, for an even smaller size of minidenticons :grin:
+
 ### Usage
 
 ```typescript

minidenticons.js

@@ -35,7 +35,8 @@ export function identicon(username, saturation=DEFAULT_SATURATION, lightness=DEF
 }
 
 export const identiconSvg =
-    globalThis.customElements?.define('identicon-svg',
+    // optional chaining only available on node 14+
+    globalThis.customElements && /*@__PURE__*/customElements.define('identicon-svg',
         class extends HTMLElement {
             constructor() { super() }
             connectedCallback() { this.identiconSvg() }