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