Add browser support (#9)

Co-authored-by: Sindre Sorhus <sindresorhus@gmail.com>

browser.js

@@ -0,0 +1,10 @@
+export default function timeSpan() {
+	const start = performance.now();
+
+	const end = () => performance.now() - start;
+	end.rounded = () => Math.round(end());
+	end.seconds = () => end() / 1000;
+	end.nanoseconds = () => end() * 1000000;
+
+	return end;
+}

package.json

@@ -11,7 +11,11 @@
 		"url": "https://sindresorhus.com"
 	},
 	"type": "module",
-	"exports": "./index.js",
+	"exports": {
+		"types": "./index.d.ts",
+		"node": "./index.js",
+		"default": "./browser.js"
+	},
 	"engines": {
 		"node": ">=12"
 	},
@@ -20,6 +24,7 @@
 	},
 	"files": [
 		"index.js",
+		"browser.js",
 		"index.d.ts"
 	],
 	"keywords": [

readme.md

@@ -2,6 +2,8 @@
 
 > Simplified high resolution timing
 
+Uses [`process.hrtime`](https://nodejs.org/api/process.html#processhrtimebigint) in Node.js and [`performance.now`](https://developer.mozilla.org/en-US/docs/Web/API/Performance/now) in browsers ([accurate to 5 microseconds](https://developer.mozilla.org/en-US/docs/Web/API/DOMHighResTimeStamp)).
+
 ## Install
 
 ```