Add breadcrumbs navigation

[carlosgmartin]

Context

This theme is missing an option to show breadcrumbs for navigation.

Proposal

Add an option to show breadcrumbs for navigation by setting "show_breadcrumbs": True under html_theme_options.

Examples:

• https://sphinxdocs.ansys.com/release/0.9/user_guide/options.html#show-breadcrumbs
• https://sphinxawesome.xyz/how-to/configure/#id5
• https://vsalvino.github.io/sphinx-library/customize.html#theme-options