foundations-of-private-computation/README: Add Windows Prerequisites.

[juharris]

Description

Add Windows Prerequites

Affected Dependencies

How has this been tested?

Tested on my Windows 10 machine.

Checklist

• [x] I have followed the Contribution Guidelines and Code of Conduct
• [ ] I have commented my code following the OpenMined Styleguide
• [ ] I have labeled this PR with the relevant Type labels
• [ ] My changes are covered by tests

[mcleonard]

Thank you!