Add social cards for mkdocs

[devraj]

Is your feature request related to a problem? Please describe. Nope, just a quick enhancement to the mkdocs configuration.

Describe the solution you'd like We already have assets for our social presence, we should add these to the mkdocs configuration:

• How to Create Social Preview Cards in MkDocs Material
• Github repository for the video above

Describe alternatives you've considered NA

Additional context This is very particular to mkdocs-material.

Thanks you @squidfunk for mkdocs-material and @james-willett for the tutorial