Add/improve documentation using mkdocs

[SarahAlidoost]

Description

closes #263 closes #215 closes #222 closes #204 closes #167 closes #93 closes #167

Checklist

• [ ] Add a reference to related issues.
• [ ] @mentions of the person or team responsible for reviewing proposed changes.
• [ ] This pull request has a descriptive title.
• [ ] Code is written according to the guidelines.
• [ ] The checks by MISS_HIT style checker and linter, below the pull request, are successful (green).
• [ ] Documentation is available.
• [ ] Add changes to the changelog file under section Unreleased.
• [ ] Model runs successfully.
• [ ] Ask a meinatainer to re-generate exe file if matlab codes are changed. About how to create an exe file, see exe readme.