Update access_transformer.md

docs/forge_loom/access_transformer.md

@@ -12,3 +12,18 @@ parent: Architectury Loom
 Access Transformers must be created in `META-INF/accesstransformer.cfg`, in MCP and SRG mappings. (Basically keep your ATs from Forge, don't remap them)
 
 You may also refer to the [Forge Documentation](https://mcforge.readthedocs.io/en/latest/advanced/accesstransformers/) on this topic if you are new to this.
+
+For forge code(if method above doesn't work):
+```groovy
+  loom {
+    forge {
+        accessTransformer(file('src/main/resources/META-INF/accesstransformers.cfg'))
+    }
+  }
+```
+For fabric code(if `fabric.mod.json` doesn't work): 
+```groovy
+  loom {
+    accessWidenerPath = file("src/main/resources/accesstransformer.accesswidener")
+  }
+```