Getting started with embedded RISC-V tutorial

# Tutorial for SymbiFlow with embedded RISC-V

# Brief explanation

Write a tutorial for getting started with SymbiFlow on an embedded RISC-V CPU on a small FPGA with Zephyr.

## Expected results

An easily reproducible tutorial which enables people to work with SymbiFlow on a relatively simple yet useful example system.

# Detailed Explanation

SymbiFlow can already work with Zephyr-enabled SoCs like LiteX/VexRiscv. Targeting Lattice iCE40, write a tutorial that lets people compile Zephyr, a bitstream that can run it, and then program an FPGA to see it in practice. As a second track, enable the same software to be run in Renode without modification if someone does not have an FPGA yet wants to work on the software side of things.

# Knowledge Prerequisites

* Sphinx
* bash