Do you want to receive Telegram notifications, when your repository gets new issues/PRs?

1. Create a Telegram bot using @BotFather.
2. Open your bot and click on the start button; bots cannot send messages unless your start a conversation with them.
3. Add the required secrets to your repository: BOT_TOKEN and USER_ID. The second one is the receiver's id and you can get yours by using the @get_id_bot bot.
4. Create your workflow file:

# .github/workflows/notify.yml
name: telegram-notifier
on:
  pull_request:
    types: [opened]
  issues:
    types: [opened]
jobs:
  something:
    runs-on: ubuntu-latest
    steps:
      - name: Blue Octocat            
        uses: muhammadmp97/[email protected]
        with:
          bot_token: ${{ secrets.BOT_TOKEN }}
          user_id: ${{ secrets.USER_ID }}

You may create an issue to test the workflow if it works properly.