Update PHP version requirement in readme

[jmejmejme]

Describe the bug

In the readme file and on the wordpress.org plugin page, "Requires PHP: 5.6"

In composer.php:

"config": {
		"platform": {
			"php": "7.4"

Installing the plugin in any PHP version lower than 7.2 results in a critical error printing a message from vendor/composer/platform_check.php

Site information

Popup Maker version: 1.20.2

WordPress version: 6.2

PHP version: <7.2.0

Expected behavior

PHP version requirement in the readme should reflect plugin requirements

Current behavior

PHP version requirement does not reflect actual plugin requirements

Steps to reproduce

1. Install plugin in a WordPress site running on a PHP version lower than 7.2.0

Additional context

Requiring PHP 7.2 or 7.4 is totally reasonable! Just a nudge to update the readme.

[danieliser]

How exactly are you installing the plugin? These checks are not run normal installation methods, so I'm assuming your using composer to manage plugins etc.

Unforutnately we can't just yet, the only option would be to remove the platform requirement entirely, but moving it to match the readme was leading to dev dependency issues on some of our tooling.

We are planning to move the plugins requirements to 7.4 in the near future... BUT... our tooling requires PHP 7.4 now.

The goal is within the next 2 major versions to be fully to PHP v7.4+ & WP v6.4.