feat: add export via ccv3 charx and json

src/ts/storage/globalApi.ts

@@ -1144,7 +1144,7 @@ export function getModelMaxContext(model:string):number|undefined{
     return undefined
 }
 
-class TauriWriter{
+export class TauriWriter{
     path: string
     firstWrite: boolean = true
     constructor(path: string){
@@ -1560,4 +1560,19 @@ export function updateHeightMode(){
             root.style.setProperty('--risu-height-size', '100%');
             break
     }
+}
+
+export class BlankWriter{
+    constructor(){
+    }
+    async init(){
+        //do nothing, just to make compatible with other writer
+
+    }
+    async write(key:string,data:Uint8Array|string){
+        //do nothing, just to make compatible with other writer
+    }
+    async end(){
+        //do nothing, just to make compatible with other writer
+    }
 }