Simplify the replaceAll polyfill setup

Author: pimterry

package-lock.json

@@ -36,7 +36,6 @@
     "@radix-ui/react-tooltip": "^1.0.7",
     "@wyw-in-js/babel-preset": "^1.0.6",
     "@wyw-in-js/transform": "^1.0.6",
-    "core-js": "^3.47.0",
     "date-fns": "^1.29.0",
     "fs-extra": "^6.0.0",
     "gray-matter": "^4.0.3",

package.json

@@ -2,8 +2,22 @@
 
 // Polyfill for older browsers (more common here than we'd expect, due to testing
 // on old Android emulators etc):
-import 'core-js/actual/string/replace-all';
+if (!String.prototype.replaceAll) {
+    String.prototype.replaceAll = function (
+        this: string,
+        search: string | RegExp,
+        replacement: string | ((substring: string, ...args: unknown[]) => string),
+    ) {
+        if (search instanceof RegExp) {
+            if (!search.global) {
+                throw new TypeError('String.prototype.replaceAll called with a non-global RegExp argument');
+            }
+            return this.replace(search, replacement as string);
+        }
+        return this.split(search).join(replacement as string);
+    } as typeof String.prototype.replaceAll;
+}
 
 export function Polyfills() {
     return null;
-}
+}