🪪mkdocs: social cards (#1428)

* 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

.github/workflows/mkdocs.yaml

@@ -22,4 +22,6 @@ jobs:
             mkdocs-material-
       - run: pip install mkdocs-material 
       - run: pip install mkdocs-nav-weight
+      - run: pip install mkdocs-publisher
+      - run: pip install mkdocs-exclude
       - run: mkdocs gh-deploy --force