test: add initial test files and component stubs

src/__tests__/utils.test.ts

@@ -0,0 +1,16 @@
+import { dateToDigital, digitalToDate, dateToBerlin, berlinToDate } from '../utils';
+
+describe('Utils', () => {
+  it('dateToDigital returns correct format', () => {
+    // TODO
+  });
+  it('digitalToDate returns a Date', () => {
+    // TODO
+  });
+  it('dateToBerlin returns a BerlinClock', () => {
+    // TODO
+  });
+  it('berlinToDate returns a Date', () => {
+    // TODO
+  });
+});