refactor: more TS code

src/react-app-env.d.ts

@@ -1,6 +1,7 @@
 /// <reference types="node" />
 /// <reference types="react" />
 /// <reference types="react-dom" />
+/// <reference types="react-scripts" />
 
 declare namespace NodeJS {
   interface ProcessEnv {
@@ -61,3 +62,6 @@ declare module "*.module.css" {
   const classes: { readonly [key: string]: string };
   export default classes;
 }
+interface Window {
+  ethereum: any;
+}