fix(Build): Use public_path script while also having publicPath set to auto.

We still need to use the ``src/public_path.js`` script as first import in our bundles to correctly resolve the loading path for chunks.
publicPath set to auto does not work in certain environments (e.g. the Plone resource registry).

Partially reverts 1b61431, "Use automatic publicPath determination instead of manually setting it."

Author: thet

src/public_path.js

@@ -1,6 +1,13 @@
-// BBB: Replaced by: ``output.publicPath = "auto"``
-// NOTE: This file will be removed in an upcoming release.
 // NOTE: Import this file before any other files
 // Overwrite path to load resources or use default one.
-__webpack_public_path__ = // eslint-disable-line no-undef
-    window.__patternslib_public_path__ || document.currentScript.src + "/../";
+__webpack_public_path__ = window.__patternslib_public_path__; // eslint-disable-line no-undef
+// eslint-disable-next-line no-undef
+if (!__webpack_public_path__) {
+    // Get chunks path from current script.
+    let src = document.currentScript?.src;
+    if (src) {
+        src = src.split("/");
+        src.pop();
+        __webpack_public_path__ = src.join("/") + "/"; // eslint-disable-line no-undef
+    }
+}