docs: add versioned docs (#1)

website/versioned_docs/version-2.6/installation.md

@@ -0,0 +1,28 @@
+---
+id: installation
+title: Installation
+sidebar_label: Installation
+slug: /
+---
+
+```bash
+$ npm i nestjs-telegraf telegraf
+```
+
+Once the installation process is complete, we can import the `TelegrafModule` into the root `AppModule`.
+
+```typescript title="src/app.module.ts"
+import { Module } from '@nestjs/common';
+import { TelegrafModule } from 'nestjs-telegraf';
+
+@Module({
+  imports: [
+    TelegrafModule.forRoot({
+      token: 'TELEGRAM_BOT_TOKEN',
+    })
+  ],
+})
+export class AppModule {}
+```
+
+The `forRoot()` method accepts the same configuration object as Telegraf class constructor from the Telegraf package, as described [here](https://telegraf.js.org/#/?id=constructor).