Add unittest package

[mohanson]

Added a unit testing library to help developers test their dapps.

Note:

1. I am not a professional JS developer. This is a general-purpose unit test package for developing on-chain scripts. You can choose to refactor this code to make it more useful and readable.
2. Subsequent maintenance is the responsibility of ccc developers.

[changeset-bot]

⚠️ No Changeset found

Latest commit: c4d40e1

Merging this PR will not cause a version bump for any packages. If these changes should not result in a new version, you're good to go. If these changes should result in a version bump, you need to add a changeset.

This PR includes no changesets

When changesets are added to this PR, you'll see the packages that this PR includes changesets for and the associated semver types

Click here to learn what changesets are, and how to add one.

Click here if you're a maintainer who wants to add a changeset to this PR