feat(nginx): add support for nginx v1.19

[damienwebdev]

PR Checklist

Please check if your PR fulfills the following requirements:

• The commit message follows our guidelines: https://github.com/graycoreio/mage2docker/blob/master/CONTRIBUTING.md#commit
• Tests for the changes have been added (for bug fixes / features)
• Docs have been added / updated (for bug fixes / features)

PR Type

What kind of change does this PR introduce?

[ ] Bugfix
[x] Feature
[ ] Code style update (formatting, local variables)
[ ] Refactoring (no functional changes, no api changes)
[ ] Build related changes
[ ] CI related changes
[ ] Documentation content changes
[ ] Other... Please describe:

What is the current behavior?

Currently, the hostname and various other behaviors are hardcoded into the container and Nginx configuration. Additionally, there's no 1.19 support.

Fixes: N/A

What is the new behavior?

This adds support for simple environment variables to configure minor details of the nginx configuration and provides an nginx v1.19 image.

Does this PR introduce a breaking change?

[x] Yes
[ ] No

I've dropped support for the v1.17 container. The v1.18 container (and v1.19) are backward compatible, simply update to the new versions.

Other information