Add Bot API 10.2 Bot Subscriptions support example

New BotSubscriptionsBot demonstrating the 36.0.0 subscription-updates API:
- onBotSubscriptionUpdated trigger reading user / invoicePayload / state
- exhaustive handling of the typed BotSubscriptionUpdated.State sealed type
  (Active / Canceled / Failed data objects + Unknown value-class fallback)
- botSubscriptionUpdatedUpdatesFlow raw update flow
- waitBotSubscriptionUpdated expectation

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

BotSubscriptionsBot/build.gradle

@@ -0,0 +1,21 @@
+buildscript {
+    repositories {
+        mavenCentral()
+    }
+
+    dependencies {
+        classpath "org.jetbrains.kotlin:kotlin-gradle-plugin:$kotlin_version"
+    }
+}
+
+apply plugin: 'kotlin'
+apply plugin: 'application'
+
+mainClassName="BotSubscriptionsBotKt"
+
+
+dependencies {
+    implementation "org.jetbrains.kotlin:kotlin-stdlib:$kotlin_version"
+
+    implementation "dev.inmo:tgbotapi:$telegram_bot_api_version"
+}