Update README examples for Flowbite 4

The color style names were replaced in flowbite-components v0.1.4 with
the Flowbite 4 style semantic names.

Author: koppen

README.md

@@ -91,12 +91,12 @@ If you want to use one of the other [Flowbite themes](https://flowbite.com/docs/
 <% end %>
 
 <!-- Outline button with color -->
-<%= render Flowbite::Button::Outline.new(style: :blue) do %>
+<%= render Flowbite::Button::Outline.new(style: :success) do %>
   Outline Button
 <% end %>
 
 <!-- Pill button -->
-<%= render Flowbite::Button::Pill.new(style: :green) do %>
+<%= render Flowbite::Button::Pill.new(style: :danger) do %>
   Pill Button
 <% end %>
 ```