* mkdocs plugins: add plugin for social cards and plugin that allow to exclude a folder
* docs: fix hyperlinks
* mkdocs: social cards (descriptions) for 'contributions' and 'deployment' guides
* mkdocs: social cards (descriptions) for all 'index.md'
* mkdocs: social cards (descriptions) for 'features' and 'plugins'
* mkdocs: social cards (descriptions) for 'general_info'
* mkdocs: social cards (descriptions) for 'configuration'
* mkdocs: social cards (descriptions) for 'installation'
* mkdocs: minor fixes
* update librechat.svg
* update how_to_contribute.md
add reference to the official GitHub documentation
