Update compatibility note in README.md

Author: meyfa

README.md

@@ -8,10 +8,6 @@ required assertions that allow you do to so.
 It supports comparing **files on disk** as well as **image resources** in
 memory.
 
-**Compatibility note:** The 2.x version of this library supports PHP versions of at least 7.2. It
-supports PHPUnit versions of at least 8.0. If you require support for older versions of PHPUnit and/or PHP,
-you will need to use version 1.x of this library.
-
 ## Installation
 
 Add this package to your Composer dev-dependencies:
@@ -20,6 +16,14 @@ Add this package to your Composer dev-dependencies:
 composer require --dev meyfa/phpunit-assert-gd
 ```
 
+**Compatibility table**
+
+| AssertGD version | Supported PHP version | Supported PHPUnit version |
+| :--------------- | :-------------------- | :------------------------ |
+| 3.*              | >= 7.3                | 9                         |
+| 2.*              | >= 7.2                | 8                         |
+| 1.*              | >= 5.3.3              | 4.8.36 - 6.5.0            |
+
 ## Examples
 
 The assertions are available as a