Documentation overhaul

[thibaudcolas]

Description

Reorganises the current documentation into separate pages in the new mkdocs website, so it’s all easier to navigate. Adds much more content based on things that are known to work well on projects, as well as references of DPL’s API, and known issues / limitations.

Fixes #86. Fixes #105. Fixes #98. Fixes #118.

Checklist

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• I have added an appropriate CHANGELOG entry