[ENHANCEMENT]: generate documentation with phpdoc

[jessevz]

Description

To generate documentation on a function level we can use phpdoc (https://docs.phpdoc.org/guide/getting-started/generating-documentation.html). This way we can automatically generate documentation based on the phpdoc comments.

• Add phpdoc for relevant functions that don't have phpdoc yet
• Automatically generate the documentation when code has been pushed

With a template (https://packagist.org/packages/automattic/phpdoc-markdown) it should then also be possible to generate the documentation in markdown format to get it in the same format as the other documentation.