Create Documentation in Sphinx reStructuredText Format.

[th4ruka]

Description of problem:

• Current user documentation (reference) of tinyweb is included in the README.md file itself.
• I feel it makes README.md cluttered. Also, with the addition of new features to the project, documentation will also be expanded.
• Therefore, I think it is more convenient to make the documentation separately, rather than including it in the README.md.

Expected:

• [ ] Create a separate directory called docs/ inside the root directory of the project.
• [ ] Use Sphinx and reStructuredText (reST) to create the documentation within docs/ directory.

Sphinx and reStructuredText (reST) is the same tool used by Micropython project. This tool makes it easier to convert the content in docs/ into different formats like HTML or PDF.

[th4ruka]

I'd be happy to help with this documentation improvement.