Create Suffix.md

[dhruvshah8]

Guide for suffix(while: ) function

Provides example, implementation and design of suffix(while: ) function.

Taken from:
#80

Checklist

• I've added at least one test that validates that my change is working, if appropriate
• I've followed the code style of the rest of the project
• I've read the Contribution Guidelines
• I've updated the documentation if necessary

[xwu]

👍

Make sure you run a spell checker on the text to catch typos, but otherwise it reads pretty well.

[natecook1000]

Looks great, @dhruvshah8 — thanks for the contribution! 🎉