Elgandoz patch 1 (#1)

[elgandoz]

Add automatic prefix based on title.

let toc = initTOC({
  selector: 'h2',
  prefix: true
})

The above code will generate links like #this-is-the-header-title. It maintains all the previous behaviours and defaults.

The convertToUrl() logic is taken from this answer.

It requires minification for the dist folder.