Feature/add feature overview section + diagram updates

[exequielrafaela]

What?

Commits on Jan 5, 2022

• updating mkdocs to latest versions + minor updates in .github files - @exequielrafaela
• adding and updating diagrams - @exequielrafaela
• updating paths for new doc structure - @exequielrafaela
• files moved under how-it-works/design/ to follow the ui doc structure sections and sub-sections - @exequielrafaela
• how-it-works/features section updated - @exequielrafaela
• moving files under /desing folder - @exequielrafaela
• adding user-guide/features overview section - @exequielrafaela

Why?

• Keeping documentation updated.
• Moving forward with https://github.com/binbashar/le-tf-infra-aws/issues/223