test: adding tests for runtime.ts. Modified README since we switched to vitest

[ai16z-demirix]

Relates to:

https://github.com/ai16z/eliza/issues/187

Risks

Low: adding tests for runtime.ts

Background

What does this PR do?

This PR adds tests for runtime.ts

What kind of change is this?

Adding new tests.

Contributing to have stable and good SDEC.

Documentation changes needed?

Minimal: Edited tests README file since we switched to vitests from jest.

Testing

Where should a reviewer start?

packages/core/

Detailed testing steps

navigate to directory and run pnpm install and pnpm test

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

see 8 files with indirect coverage changes