Add MRI3.2 to supported versions documentation

Author: niku

README.md

@@ -16,7 +16,7 @@ boot it every time you run a test, rake task or migration.
 
 ## Compatibility
 
-* Ruby versions: MRI 2.7, MRI 3.0, MRI 3.1
+* Ruby versions: MRI 2.7, MRI 3.0, MRI 3.1, MRI 3.2
 * Rails versions: 6.0, 6.1, 7.0
 * Bundler v2.1+