fix(): fix type declarations

Author: Ian Tan

typings/json.d.ts

@@ -0,0 +1,4 @@
+declare module '*.json' {
+  var exported: any;
+  export = exported;
+}

typings/window.d.ts

@@ -0,0 +1,7 @@
+import Zilliqa from '../src/zilliqa';
+
+declare global {
+  interface Window {
+    Zilliqa: typeof Zilliqa;
+  }
+}