update docs with macos platform

[jrwren]

Steps

• Add your name or username and a link to your GitHub profile into the Contributors.md file.
• Build the project on your machine. If it does not compile, fix the errors.
• Describe the purpose and approach of your pull request below.
• Submit the pull request. Thank you very much for your contribution!

Purpose

Include macos platform
For issue #8

Approach

Update docs.

[david-swift]

Thanks!