doc: readme revision

[myungjin]

Description

To reflect changes made in v0.1.0, the top-level README.md is revised. Also, the description for examples is updated to highlight that the multiworld examples are fault-tolerant.

Type of Change

• [ ] Bug Fix
• [ ] New Feature
• [ ] Breaking Change
• [ ] Refactor
• [x] Documentation
• [ ] Other (please describe)

Checklist

• [ ] I have read the contributing guidelines
• [ ] Existing issues have been referenced (where applicable)
• [ ] I have verified this change is not present in other open pull requests
• [ ] Functionality is documented
• [ ] All code style checks pass
• [ ] New code contribution is covered by automated tests
• [ ] All new and existing tests pass