Update to 1.21 & Add exclusion list

- Iris' shader selection screen is excluded by default
- Also added unifiedPublishing for easier update publishing

settings.gradle

@@ -4,6 +4,7 @@ pluginManagement {
             name = 'Fabric'
             url = 'https://maven.fabricmc.net/'
         }
+        maven { url "https://maven.architectury.dev/" }
 		mavenCentral()
         gradlePluginPortal()
     }