fixes/fill of docs

plugin/src/main/kotlin/dev/inmo/plagubot/Plugin.kt

@@ -25,9 +25,19 @@ interface Plugin {
         database: Database,
         params: JsonObject
     ) {}
+
+    /**
+     * Override this method in cases when you want to declare common bot behaviour. In case you wish to use FSM, you
+     * should override the method with receiver [BehaviourContextWithFSM]
+     */
     suspend fun BehaviourContext.setupBotPlugin(
         koin: Koin
     ) {}
+    /**
+     * Override this method in cases when you want to declare full behaviour of the plugin. It is recommended to declare
+     * common logic of plugin in the [setupBotPlugin] with [BehaviourContext] receiver and use override this one
+     * for the FSM configuration
+     */
     suspend fun BehaviourContextWithFSM<State>.setupBotPlugin(koin: Koin) {
         (this as BehaviourContext).setupBotPlugin(koin)
     }