Add a warning about ABI

Author: ileasile

jupyter-lib/api/src/main/kotlin/org/jetbrains/kotlinx/jupyter/api/libraries/LibraryDefinitionImpl.kt

@@ -12,7 +12,9 @@ import org.jetbrains.kotlinx.jupyter.api.RendererTypeHandler
 /**
  * Trivial implementation of [LibraryDefinition].
  * You may use it in simple cases instead of overriding [LibraryDefinition]
- * to avoid additional anonymous classes creation
+ * to avoid additional anonymous classes creation.
+ * Tend to use [JupyterIntegration] instead: in this case ABI will not break
+ * after every new property addition.
  */
 class LibraryDefinitionImpl(
     override val dependencies: List<String> = emptyList(),