feat: Adding unit tests for start - Covering goals, defaultCharacters, relationships, evaulators, posts, database, messages

[ai16z-demirix]

Relates to:

https://github.com/ai16z/eliza/issues/64 https://github.com/ai16z/eliza/issues/340

Risks:

low - Only tests are affected

Background:

Unit tests as a starter

What does this PR do?

Includes tests for core package

What kind of change is this?

Improvements/Features

Adding basic unit tests is a good starter for having good Testing/Quality Assurance process

Documentation changes needed?

Yes, but not in the main Documentation, README-TESTs.md is added for test documentation

Testing:

Running the tests and making sure they are valid.

Where should a reviewer start?

In packages/core

Detailed testing steps:

Navigating to packages/core folder, runing pnpm install, pnpm test to run tests