Fix typographical errors on the documentation

[0x2b3bfa0]

Issue

Fixes #97

Description

This pull request fixes some typographical errors on the documentation.

Testing

Proofreading should be enough.

Checklist

• 🤔 CONSIDER adding a unit test if your PR resolves an issue.
• ✅ DO check open PR's to avoid duplicates.
• ✅ DO keep pull requests small so they can be easily reviewed.
• ✅ DO build locally before pushing.
• ✅ DO make sure tests pass.
• ✅ DO make sure any new changes are documented.
• ✅ DO make sure not to introduce any compiler warnings.
• ❌AVOID breaking the continuous integration build.
• ❌AVOID making significant changes to the overall architecture.

[ghost]

All CLA requirements met.

[keithrfung]