Add Schema.org markup

[dunglas]

Add the following Schema.org markup to all the pages (including the main page):

• https://schema.org/WebPage

Add the following to all docs page:

• https://schema.org/CreativeWork

https://github.com/dunglas/calavera can be used to extract the relevant metadata from the Git repository. Creating an integration between Calavera and Gastby (a Calavera transformer) would be the best solution.

Calavera is able to generate directly the proper JSON-LD markup (related to #60 and #61).

[teohhanhui]

https://schema.org/TechArticle instead of https://schema.org/CreativeWork

[dunglas]

Indeed, Calavera needs an update.