TP157110: Add requirement for lowest supported php version

[award28]

Description

Adds our currently lowest supported version as a requirement in our composer.json file.

Manual Testing Steps

1.

Pre-Submission Checklist:

• [ ] You've updated the CHANGELOG following the steps here
• [ ] Internal Only - If this is a release, have you:
  • [ ] Updated the links in the CHANGELOG to point towards the new versions
  • [ ] Incremented the version in the following places: module.xml and composer.json

[klaviyobot]

https://klaviyo.tpondemand.com/entity/157110