fix: speed up initial client bundling

Author: alexander-akait

client-src/utils/getCurrentScriptSource.js

@@ -1,4 +1,30 @@
-import getCurrentScriptSource from "./getCurrentScriptSource.js";
+/**
+ * @returns {string}
+ */
+function getCurrentScriptSource() {
+  // `document.currentScript` is the most accurate way to find the current script,
+  // but is not supported in all browsers.
+  if (document.currentScript) {
+    return document.currentScript.getAttribute("src");
+  }
+
+  // Fallback to getting all scripts running in the document.
+  const scriptElements = document.scripts || [];
+  const scriptElementsWithSrc = Array.prototype.filter.call(
+    scriptElements,
+    (element) => element.getAttribute("src"),
+  );
+
+  if (scriptElementsWithSrc.length > 0) {
+    const currentScript =
+      scriptElementsWithSrc[scriptElementsWithSrc.length - 1];
+
+    return currentScript.getAttribute("src");
+  }
+
+  // Fail as there was no script to use.
+  throw new Error("[webpack-dev-server] Failed to get current script source.");
+}
 
 /**
  * @param {string} resourceQuery