refactor SEO component according to social media and Google tutorial

[stephenlprice]

Here is the tutorial: https://www.gatsbyjs.com/tutorial/seo-and-social-sharing-cards-tutorial/

Docs on SEO for Gatsby: https://www.gatsbyjs.com/docs/how-to/adding-common-features/seo/

Test results with this Google tool: https://search.google.com/test/rich-results
https://support.google.com/webmasters/answer/7552505?hl=en

https://www.gatsbyjs.com/tutorial/seo-and-social-sharing-cards-tutorial/

https://search.google.com/test/rich-results