Add readme and need for closest polyfill

README.md

@@ -1 +1,35 @@
-# accessibilityjs
+# accessibilityjs
+
+Client side accessibility error scanner.
+
+## Usage
+
+```javascript
+import scanForProblems from 'accessibilityjs'
+
+function logError(error, onPageWarning = true) {
+  error.element.addEventListener('click', function () {
+    alert(`${error.name}\n\n${error.message}`)
+  }, {once: true})
+
+  if (onPageWarning) error.element.classList.add('accessibility-error')
+}
+
+document.addEventListener('ready', function() {
+  scanForProblems(document, logError)
+})
+```
+
+## Browser support
+
+- Chrome
+- Firefox
+- Safari
+- Internet Explorer 11+
+- Microsoft Edge
+
+Internet Explorer and Edge require a polyfill for [`closest`](https://developer.mozilla.org/en-US/docs/Web/API/Element/closest#Polyfill).
+
+## Development
+
+Test script changes with `test.html`.