PHP-Activate 0.3.1

I've released php-activate 0.3.1, a PHP project version manager for Linux systems using native PHP packages.

Made for those working with multiple projects using a variety of PHP versions, this script will switch to the correct PHP version for the local shell session. It does not require sudo, so even works in IDEs.

The latest version contains a few small changes:

Eliminate the activate_php:export:20: invalid option(s) output. Exporting the php function is not needed as we source the script into the current shell session.

Harden the script by implementing shellscript linting recommendations.

Readme update.