Annotate `qiskit.org` with `schema.org` markup

[IceKhan13]

Feature description

In order to provide better transparency and search optimization to our pages it would be great to annotate pages of qiskit.org with schema.org markup tools.

There are hundreds of types of annotations, which will enable better user experience when searching for information about Qiskit.

Look at example of schema for Target corporation to get a sense what it will provide from visual perspective (not talking about better search optimization).

Vue component for schema already exists. It need to be reviewed and integrated if acceptable. https://github.com/vueuse/schema-org

Additional context

Schema.org is a collaborative, community activity with a mission to create, maintain, and promote schemas for structured data on the Internet, on web pages, in email messages, and beyond.

Schema.org is a reference website that publishes documentation and guidelines for using structured data mark-up on web-pages (called microdata). Its main objective is to standardize HTML tags to be used by webmasters for creating rich results (displayed as visual data or infographic tables on search engine results) about a certain topic of interest