Add PHP 7.3

[Mapsred]

Description

A new version of PHP 7 was released today

Type of change

Add PHP 7.3 version

Please delete options that are not relevant.

• [ ] Bug fix (non-breaking change which fixes an issue)
• [X] New feature (non-breaking change which adds a functionality)
• [ ] Breaking change (fix or feature that would cause existing functionality to not work as expected)

Which area/features are impacted ?

php-fpm container

[fdespier]

Hi, this tag was release 6 days ago :) https://github.com/docker-library/php/blob/3c64c61733a19863c5283f3f336add33dd298eeb/7.3/stretch/fpm/Dockerfile

[lbassin]

Thank you! :)