Add message events

[moisses89]

Closes #63

• Add events to readme
• Add events test

[Uxio0]

Why is this required?

[moisses89]

because this line was not passing https://github.com/safe-global/safe-events-service/pull/66/files#diff-d79512aca03ad68a51d5b4e98066338dcb424638d13712a3f0b9d909ba23ee63R80
looks like mock keep the number of calls between tests.

[Uxio0]

This does not sound right, as we are using mocks for same functions and I didn't have to do that, like

safe-events-service/src/routes/webhook/webhook.service.spec.ts

Line 23 in b112382

const findAllActiveSpy = jest

This mock is set up again in the next test

I'm not an expert here, so if you think there's no other way around we can do it, but sounds weird

[moisses89]

I did it at different way, the issue was that the mock webhookService was declared globally out of beforeEach and the spyOn uses this object that was declared globally, consequently the calls are accumulated between tests.