update behaviour builder fsm readme

tgbotapi.behaviour_builder.fsm/README.md

@@ -2,7 +2,31 @@
 
 [![Maven Central](https://maven-badges.herokuapp.com/maven-central/dev.inmo/tgbotapi.behaviour_builder.fsm/badge.svg)](https://maven-badges.herokuapp.com/maven-central/dev.inmo/tgbotapi.behaviour_builder.fsm)
 
+## What is it?
+
+
 This extension has been created to integrate finite state machine in [BehaviourBuilder](../tgbotapi.behaviour_builder/README.md).
 In case you wish to use some custom store for steps (states), you may extend `StatesManager` or use `DefaultStatesManager`
 with custom `DefaultStatesManagerRepo`. See [Examples repo](https://github.com/InsanusMokrassar/TelegramBotAPI-examples/tree/master/FSMBot)
-to get more info and see how it works on base level
+to get more info and see how it works on base level.
+
+Lets see several examples:
+
+```kotlin
+data class StateRealization(override val context: ChatId) : State
+
+bot.telegramBotWithBehaviourAndFSMAndStartLongPolling(TOKEN) {
+    strictlyOn<StateRealization> {
+        // here your logic of state
+        it // you must return from state handler some other state as a result of this one or null if you want to complete the chain
+    }
+
+    onCommand("start") {
+        startChain(StateRealization(it.chat.id)) // starting of chain with StateRealization state
+    }
+}
+```
+
+Currently, for the states there is only one restriction - your state must implements `State` interface and override `context` to define it. It may be important that `context` will be used under the hood for comparison with contexts of other states in some situations in it may be important to correctly realize `equals` method.
+
+It is important, that all other methods are the same as for [BehaviourBuilder](../tgbotapi.behaviour_builder/README.md).