Improve documentation for `@semaphore/data` package

[0xjei]

Description

This PR aims at improving the documentation (code / README) for the @semaphore/data package.

Related Issue(s)

see #483

Checklist

• [x] My code follows the style guidelines of this project
• [x] I have performed a self-review of my code
• [x] I have commented my code, particularly in hard-to-understand areas
• [ ] I have made corresponding changes to the documentation
• [x] My changes generate no new warnings
• [x] I have run yarn format and yarn lint without getting any errors
• [ ] I have added tests that prove my fix is effective or that my feature works
• [ ] New and existing unit tests pass locally with my changes
• [ ] Any dependent changes have been merged and published in downstream modules