Update composer dependencies

[TimWolla]

Care should be taken to review the changes to htmlpurifier (message processing) and emogrifier (emails).

[jens1o]

What's up with the SCSS Compiler? It reached v0.7.6, compared to the used v0.3.0 version.

[TimWolla]

An upgrade was attempted in 2016 and then reverted: https://github.com/WoltLab/WCF/commits/master/wcfsetup/install/files/lib/system/style/scssphp/scss.inc.php

The performance of newer version was horrible, if I remember correctly.

[jens1o]

I expect 3.2 to be published in early 2019, so what about giving it another try?

[Morik]

The massive performance loss is due to the utf8 support in scss indentifers added in v0.6.2.
See https://github.com/leafo/scssphp/commit/dbca8da31c3cfd5cfd9c7b2c5a0a74310fc248ae
You can disable it by calling $this->compiler->setEncoding('iso8859-1'); after initialization.
This gives you about the same performance as v0.3.0 currently used.

[Morik]

And what about scssphp?
Do you plan to stick on that outdated version?
The current version is 0.7.7...