fix: move browser to top of exports

The order of exports is important. If you want to serve a browser-specific
file, it needs to go earlier in the exports object, otherwise one
of the other exports will be matched.

In this case the file being webpacked was using require, which matched
`exports.require` before `exports.browser` so tried to require
`./src/lib.cjs`, which then throws as it tries to require `util` which
is not a dep of this module.

The solution is just to move the `browser` field in front of `require`
and `import`.

Author: achingbrain

package.json

@@ -14,9 +14,9 @@
   "types": "./src/lib.d.ts",
   "exports": {
     ".": {
+      "browser": "./src/lib.browser.js",
       "import": "./src/lib.js",
-      "require": "./src/lib.cjs",
-      "browser": "./src/lib.browser.js"
+      "require": "./src/lib.cjs"
     }
   },
   "scripts": {