Copy To functionality for notebooks (#141)

* Add Copy To functionality for notebooks

* Fix formatting

* Fix linting errors

* Fixes

* Fix build failure

* Rebase and address feedback

* Increase test coverage

src/Utils/Base64Utils.test.ts

@@ -0,0 +1,11 @@
+import * as Base64Utils from "./Base64Utils";
+
+describe("Base64Utils", () => {
+  describe("utf8ToB64", () => {
+    it("should convert utf8 to base64", () => {
+      expect(Base64Utils.utf8ToB64("abcd")).toEqual(btoa("abcd"));
+      expect(Base64Utils.utf8ToB64("小飼弾")).toEqual("5bCP6aO85by+");
+      expect(Base64Utils.utf8ToB64("à mon hôpital préféré")).toEqual("w6AgbW9uIGjDtHBpdGFsIHByw6lmw6lyw6k=");
+    });
+  });
+});

src/Utils/Base64Utils.ts

@@ -0,0 +1,7 @@
+export const utf8ToB64 = (utf8Str: string): string => {
+  return btoa(
+    encodeURIComponent(utf8Str).replace(/%([0-9A-F]{2})/g, (_, args) => {
+      return String.fromCharCode(parseInt(args, 16));
+    })
+  );
+};