docs: update contribution guidelines to add section on commit structure

docs/ruby-thing.rb

@@ -0,0 +1,12 @@
+#!/usr/bin/env ruby
+
+File.open("INSTALL.md", 'r') do |f|
+  f.each_line do |line|
+    forbidden_words = ['Table of contents', 'define', 'pragma']
+    next if !line.start_with?("#") || forbidden_words.any? { |w| line =~ /#{w}/ }
+     
+    title = line.gsub("#", "").strip
+    href = title.gsub(" ", "-").downcase
+    puts "  " * (line.count("#")-1) + "* [#{title}](\##{href})"
+  end
+end