docs(readme): Add EAP install guide (#16)

README.md

@@ -18,6 +18,13 @@ This plugin adds support for using Pest PHP inside PHPStorm
   Download the [latest release](https://github.com/pestphp/pest-intellij/releases/latest) and install it manually using
   <kbd>Preferences</kbd> > <kbd>Plugins</kbd> > <kbd>⚙️</kbd> > <kbd>Install plugin from disk...</kbd>
 
+- Using Early Access Program (EAP) builds:
+
+  <kbd>Preferences</kbd> > <kbd>Plugins</kbd> > <kbd>⚙️</kbd> > <kbd>Manage plugin repositories</kbd>
+
+  Add a new entry for [`https://plugins.jetbrains.com/plugins/eap/14636`](https://plugins.jetbrains.com/plugins/eap/14636)
+
+  Then search for the plugin and install it as usual.
 
 ---
-Plugin based on the [IntelliJ Platform Plugin Template](https://github.com/JetBrains/intellij-platform-plugin-template).
+Plugin based on the [IntelliJ Platform Plugin Template](https://github.com/JetBrains/intellij-platform-plugin-template).