Add social media icons

Social media icons are the small links to your profiles shown in your doc's footer.

By default, Luma doesn't display any social links. To add social media icons, specify the socials field in the top level of your config. You can specify GitHub, Discord, Twitter, or Slack.

socials:
  - github: https://github.com/luma-docs/luma
  - discord: https://discord.gg/yT9KPAddxw