Fifo code based on SBY quick start.
Instead of showing the full design we are (currently) focusing on a single output (rdata), using `%ci*` to get the subcircuit it relies on.
Overall structure in place to match the iCE40 flow.
Still needs a new example design, and more text for the later sections (which the counter doesn't cover).
Blocking tasks are now capital TODO (compared to non-blocking todo).
Updated some of the todos.
Added note about which intel synth does which families.
Rename extended Yosys universe to Yosys family.
Added brief text to landing page, and also a note about the restructure and where to find old docs.
Moved todolist above ToC in preparation for disabling it in the config (so that it doesn't need it's own header).
Fixed pdf build, was previously breaking on trying to include the svg badges.
Moved remaining content into relevant places.
Added `load_design.rst` to more scripting.
Split fsm handling and abc out of optimization passes. Also moved things around to match the general flow previously described.
Changed generic `synth` for `prep` instead.
Replace `typical_phases.rst` and `examples.rst` with a single `example_synth.rst`.
Also updating the counter example to match.
Aims to reduce redundancy, and simplify the getting started section.
Details on things like `proc`, `memory` and `fsm` should instead be in the advanced section (under the new `synth` subsection).
Krystine Sherwin