Telegram Auto Join-Request Bot

I want a small Telegram bot that automatically accepts every pending and future join request in my group and channels, then follows up with a single, standard welcome message. Nothing more—no member logging or database work is required.

Here’s what I expect from you:
• A clean, well-commented script (Python, Node.js or another reliable language you prefer) that can run 24/7 through a simple VPS or a cloud function.
• Clear instructions on how I install the dependencies, create the BotFather token, add the bot as an admin and launch it.
• A quick way to edit the text of the standard welcome message in case I want to change it later.

As soon as the bot is tested live in my group and it automatically approves requests and posts the welcome text, the job is done.