Add Telegram API base url for Local Bot API Server

Hi!

I use a self-hosted Telegram Bot API server, as described in the official documentation: [Using a Local Bot API Server](https://core.telegram.org/bots/api/#using-a-local-bot-api-server).

This setup requires using a custom base URL for API requests. However, when using this plugin in the runner, there doesn’t seem to be an option to change the API URL.

Could you please consider adding support for a custom Telegram Bot API URL? I think this feature could be useful for other users as well.

The issue does not name implementation files or tests. Start by locating the action entry point that builds Telegram API requests and identifies its configurable inputs; done means a custom base URL works for a local Bot API server while the default URL remains unchanged.

Written by the indexing model from the issue text.