Missing swoole onto php 7.*

*Summary**

This PR fixes :

Test plan (required)

docker run -it --rm -e "PHP_EXTENSIONS=swoole" thecodingmachine/php:7.2-v4-apache php -m | grep swoole

Checklist

[x] I followed the guidelines in CONTRIBUTING guide
[x] I have squashed any insignificant commits
[x] This change has comments for package types, values, functions, and non-obvious lines of code

thecodingmachine / docker-images-php