Refactor test files location

[leo-ori]

Summary

Relocate test files (mock data and test) inside the src folder

Fixes

#10

Proposed changes

• Move mockData folder to src/common/
• Move test folder to src/
• Add import 'jest-extended'; to index.ts to suppress errors for toIncludeAllMembers in JsonFormatter.tests.tsx
• Fix tests:
  • Replace toString with JSON.stringify and use toMatch with regular expressions.
  • Remove unnecessary scaped chars

Test

• Run all the tests yarn test
• Make sure all tests pass

[doneill]

This was introduced with #5, we will need to consider another solution as we don't want to intermix test with source when packaging the lib.

[leo-ori]

Closed in favor of #13