Build `ltitop` documentation

[hidmic]

Rationale

As of today, ltitop has no documentation. That makes it useless for pretty much anyone.

Definition of Done

• Document project public APIs
  • Use ReST format for docstrings.
• Document project itself
  • Add quickstart?
  • Add overview
  • Add purpose
  • Add tutorial?
• Build project documentation using Sphinx
  • Use RTD theme
• Use RTD to publish
  • Ensure rebuilds on push to master (use Github webhook).
• Populate README.md
  • Add short overview
  • Add project logo
  • Add badges
  • Link to docs

Additional considerations

See this blog post for useful pointers.