test: Adds SDK unit tests and CI task

[miquelbeltran]

• Adds SDK unit tests.
  • The Test file contains two basic tests:
    • 1. checks if send error worked correctly and data is passed,
    • 2. checks that the error is stored in "async storage" if the error fails to send.
• While implementing the tests, I found that some methods were not properly awaited.
• I have also setup the prettier formatter, since I got some formatting inconsistency while editing SDK files, so the PR is a big bigger than I originally planned.
• I have also setup CI jobs to run test and the prettier check, based on what we do in raygun4node.

[miquelbeltran]

Adding dev dependencies for running tests, as well as fixed the prettier command to include tests and mocks

[TheRealAgentK]

LGTM