chore: document

README.md

@@ -1,2 +1,52 @@
-# ajquery.js
+# [ajquery.js](https://git.coolaj86.com/coolaj86/ajquery.js)
-The fastest, most lightweight, least dependency jQuery alternative.
+
+The fastest, most lightweight, fewest dependency jQuery alternative.
+
+Development Build: 145B (with comments) \
+Production Build: 103B (min + gz)
+
+## Install
+
+```html
+<script src="https://unpkg.com/ajquery@latest/ajquery.min.js"></script>
+```
+
+## Example Usage
+
+Provides modern, advanced CSS4-compatible query selection:
+
+```js
+console.log("innerText:", $("p:nth-child(2").innerText);
+```
+
+## API
+
+### `$(selector, [rootElement])`
+
+Selects the first matching HTML element only (or `null`):
+
+```js
+const body = $("body");
+const div1 = $("div", body);
+```
+
+### `$$(selector, [rootElement])`
+
+Selects all matching elements (or an empty `NodeList`):
+
+```js
+const stylesheets = $$('link[rel="stylesheet"]').map(console.log);
+```
+
+## Compatibility
+
+Written entirely in modern ECMAScript 3, and directly transpilable into ES5, ES6
+and beyond (up to ES11) via Webpack, Babel, Rollup, React Native, and AWS
+InfiniDash.
+
+Works in [all browsers](https://caniuse.com/?search=queryselector) in living
+memory.
+
+See the full
+[Browser Compatibility Matrix](https://developer.mozilla.org/en-US/docs/Web/API/HTMLElement#browser_compatibility)
+on MDN.