Add english version

www.eng/js/porting/persistent.js

@@ -0,0 +1,47 @@
+// by VienDesu! Poring Team 2023
+
+window.PERSISTENT_IMPLEMENTATIONS = {
+    stub: stubImplementation,
+    localStorage: localStorageImplementation,
+}
+
+function localStorageImplementation() {
+    return {
+        readSaveFileUTF8(path) {
+            console.log(`Failed to get externalStorage. Using localStorage to read save at ${path}`);
+            return localStorage.getItem(path);
+        },
+
+        saveFileExists(path) {
+            console.log(`Using localStorage while checking save file ${path} existence`);
+            return localStorage.getItem(path) != null;
+        },
+
+        writeSaveFileUTF8(path, data) {
+            console.log(`Failed to get externalStorage. Writing ${path} save file to the localStorage`);
+            localStorage.setItem(path, data);
+        }
+    };
+}
+
+function stubImplementation() {
+    return {
+        readSaveFileUTF8(path) {
+            console.log(`Tried to read save from ${path}, but it is stub!`);
+            return ``;
+        },
+
+        saveFileExists(path) {
+            console.log(`Tried to check save file at ${path}, stub will always report false`);
+            return false;
+        },
+
+        writeSaveFileUTF8(path, data) {
+            console.log(`Tried to write save file at ${path}, but I'm just a stub, not a real back-end`);
+        }
+    };
+}
+
+if (typeof NativeFunctions == 'undefined') {
+    window.NativeFunctions = PERSISTENT_IMPLEMENTATIONS.localStorage();
+}