[doc] Improve documentation

Signed-off-by: Douglas Reis <doreis@lowrisc.org>

Author: engdoreis

README.md

@@ -1,25 +1,58 @@
-# Ftditool is a C++ implementation for SPI/I2C Flash memory communication leveraging FTDI MPSSE-enabled chips.
+# ftditool: A C++ implementation for SPI Flash and GPIO leveraging FTDI MPSSE-enabled chips.
 
-The FT4222 is supported for fast qSPI transactions.
+`ftditool` supports **SPI** and **GPIO** over **FT4222** and **FT2232** chips. The FT4222 specifically supports fast **QSPI** transactions.
 
-## Getting started
-Build:
+## Getting Started
+
+Install the dependencies using Nix or any other method:
+
+```sh
+nix develop
 ```
+
+### Build:
+```bash
 cmake -B build -S ./ && cmake --build build
 ```
-Run with --help argument for more information:
+
+### Usage:
+
+Run with the `--help` argument for more information:
+
 ```sh
 build/ftditool --help
 ```
-Read jedec:
+
+**Read JEDEC ID:**
+
 ```sh
 build/ftditool jedec
 ```
-Read page 0x800:
+
+**Read page 0x8000:**
+
 ```sh
 build/ftditool read-page --addr 0x8000
 ```
 
-## Dependency graph
+For a full list of commands:
+
+```sh
+build/ftditool --help
+```
+
+For an example of a real-world application of `ftditool`, check out the [mocha](https://github.com/lowRISC/mocha/blob/main/util/fpga_runner.py) repository.
+
+## Nix
+
+`ftditool` can be easily installed using **Nix**:
+
+```sh
+nix shell github:lowrisc/ftditool
+```
+----
+
+## Development
+### Dependency graph
 ![Dependency graph](doc/img/deps.png)