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.