Telegram Bot with Telegraf.js - Send messages to chat

I want to create a Telegram Bot with Node.js and I am using Telegraf for it. I know I can answer to messages like this:

app.hears('hi', (ctx) => ctx.reply('Hey there!'))

But how can I send a message without getting a message before? I want to read a file and always when the file got changed I want to send a message.

const Telegraf = require('telegraf');
var fs = require('fs');

const app = new Telegraf(process.env.BOT_TOKEN);

var filePath = "C:\\path\\to\\my\\file.txt";

fs.watchFile(filePath, function() {
    file = fs.readFileSync(filePath);

    // Send message to chat or group with the file content here

    console.log("File content at: " + new Date() + " is: \n" + file);
})

Would be nice if someone can help me with it.

via Nono