Allow configuration of installation page via meta-data (front-matter)

[froschdesign]

Currently, the automatic generation of the installation page is configured via the MkDocs configuration file (mkdocs.yml) but it would be more intuitive to insert this directly into the related file.

Current Usage

mkdocs.yml

extra:
    project: Components
    installation:
        config_provider_class: 'Laminas\Cache\ConfigProvider'
        module_class: 'Laminas\Cache\Module'

https://github.com/laminas/laminas-cache/blob/070f1942d031abb8ce976e3cfdbd74a2674655c8/mkdocs.yml#L40-L44

Preferred Usage

installation.md:

---
config_provider_class: Laminas\Cache\ConfigProvider
module_class: Laminas\Cache\Module
---

# This Is Only a Placeholder

The content of this page can be found under:

https://github.com/laminas/documentation-theme/blob/master/theme/pages/installation.html

https://www.mkdocs.org/user-guide/writing-your-docs/#meta-data