refactor: replace process.hrtime with Date.now (#176)

Switched from `process.hrtime` to `Date.now` as high-resolution timing is not required in this case. This change removes the dependency on Node.js-specific functionality, enabling the library to run in environments like Cloudflare Workers using `unenv` with Angular.

packages/critters/src/index.js

@@ -158,7 +158,7 @@ export default class Critters {
    * Apply critical CSS processing to the html
    */
   async process(html) {
-    const start = process.hrtime.bigint();
+    const start = Date.now();
 
     // Parse the generated HTML in a DOM we can mutate
     const document = createDocument(html);
@@ -191,16 +191,16 @@ export default class Critters {
 
     // serialize the document back to HTML and we're done
     const output = serializeDocument(document);
-    const end = process.hrtime.bigint();
-    this.logger.info('Time ' + parseFloat(end - start) / 1000000.0);
+    const end = Date.now();
+    this.logger.info(`Time ${end - start}ms`);
     return output;
   }
 
   /**
    * Get the style tags that need processing
    */
   getAffectedStyleTags(document) {
-    const styles = [].slice.call(document.querySelectorAll('style'));
+    const styles = [...document.querySelectorAll('style')];
 
     // `inline:false` skips processing of inline stylesheets
     if (this.options.reduceInlineStyles === false) {