Update Identifier usage to modern practices (#212)

Author: cassiancc

tags/guide/identifiers.ytag

@@ -7,12 +7,12 @@ type: text
 In your main mod class or a helper class:
 (in this example, `YourMod`)
 ```java
-public static final String MODID = "yourmod";
+public static final String MOD_ID = "yourmod";
 
 // ...
 
 public static Identifier id(String path) {
-    return new Identifier(YourMod.MODID, path);
+    return Identifier.fromNamespaceAndPath(YourMod.MOD_ID, path);
 }
 ```
 To use it: