Fix documentation for additionalRuntimeClasspath for <=1.21.9

toolchain/docs/dependencies/nonmclibs.md

@@ -34,6 +34,23 @@ dependencies {
     additionalRuntimeClasspath 'com.example:example:1.0'
 }
 ```
+:::warning
+However, using a library that has transitive dependencies will require you to manually exclude and `additionalRuntimeClasspath` / `implementation` the dependency yourself. This is only needed if that specific module is required at runtime; compilation will proceed fine.
+
+```gradle
+dependencies {
+    // This is required to add the library at compile time
+    implementation 'com.example:example:1.0'
+    // This adds the library to all the runs
+    additionalRuntimeClasspath 'com.example:example:1.0' {
+        // exclude the transitive dependency you want to add to the classpath
+        exclude 'com.example:dependency'
+    }
+    // add the module back to the classpath
+    additionalRuntimeClasspath 'com.example:my_module:1.0'
+}
+```
+:::
 
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