docs: update readme (#7)

* docs: update readme

* docs: fix github actions badge

Author: q9f

README.md

@@ -1,10 +1,77 @@
 # omniauth-ethereum
-Implements the Ethereum provider strategy for OmniAuth
 
-To test
+[![GitHub Workflow Status](https://img.shields.io/github/workflow/status/q9f/omniauth-ethereum/Test)](https://github.com/q9f/omniauth-ethereum/actions)
+[![GitHub release (latest by date)](https://img.shields.io/github/v/release/q9f/omniauth-ethereum)](https://github.com/q9f/omniauth-ethereum/releases)
+[![Gem](https://img.shields.io/gem/v/omniauth-ethereum)](https://rubygems.org/gems/omniauth-ethereum)
+[![GitHub top language](https://img.shields.io/github/languages/top/q9f/omniauth-ethereum?color=red)](https://github.com/q9f/omniauth-ethereum/pulse)
+[![GitHub](https://img.shields.io/github/license/q9f/omniauth-ethereum)](LICENSE)
+
+Authentication Strategy for [OmniAuth](https://github.com/omniauth/omniauth) to authenticate a user with an [Ethereum](https://ethereum.org) account.
+
+### Installation
+Add `omniauth-ethereum` to your `Gemspec`.
+
+```ruby
+gem 'omniauth-ethereum'
+```
+
+### Rails Usage
+1. Configure `config/routes.rb` in rails to serve the following routes:
+
+```ruby
+Rails.application.routes.draw do
+  post '/auth/:provider/callback', to: 'sessions#create'
+  post '/auth/ethereum', to: 'sessions#new'
+  root to: 'sessions#index'
+end
 ```
-bundle
-rspec
+
+2. Create a `SessionsController` for your app that enables an Ethereum authentication path.
+
+```ruby
+class SessionsController < ApplicationController
+  skip_before_action :verify_authenticity_token, only: :create
+
+  def create
+    if request.env['omniauth.auth']
+      flash[:notice] = "Logged in"
+    else
+      flash[:notice] = "Unable to log in"
+    end
+
+    redirect_to '/'
+  end
+
+  def index
+    render inline: "<%= button_to 'Sign in', auth_ethereum_path %>", layout: true
+  end
+end
 ```
 
-An [example Rails app using omniauth-ethereum](https://github.com/nahurst/omniauth-ethereum-rails)
+3. Add an Ethereum provider to your `config/initializers/omniauth.rb` middleware.
+
+```ruby
+Rails.application.config.middleware.use OmniAuth::Builder do
+  provider :ethereum
+end
+```
+
+4. Add a `notice` class to your body templates relevant for authentication.
+
+```html
+<p class="notice"><%= notice %></p>
+```
+
+### Testing
+Run the spec tests:
+
+```shell
+bundle install
+bundle exec rspec --require spec_helper
+```
+
+### Demo template
+An example Rails app using omniauth-ethereum can be found at [nahurst/omniauth-ethereum-rails](https://github.com/nahurst/omniauth-ethereum-rails).
+
+### License
+The gem is available as open-source software under the terms of the [Apache 2.0 License](LICENSE).