Add custom button to html template of ner manual.

[ines (Ines Montani)]

@rutul_gandhi

But the thing is by adding button with blocks it shows in task container, which becomes unavailable when there are no more tasks.

Ah, that's a good point! Maybe just add it in JavaScript then? Something like this:

const button = document.createElement('button')
button.style = 'position: absolute; top: 10px; right: 10px;'
button.textContent = "Stop server"
button.addEventListener('click', () => { console.log('Do something...') })
document.body.appendChild(button)