Inject fullscreen button into GitLab diffs

GitlabFullscreen.js

// ==UserScript==
// @name         GitLab Fullscreen Diffs
// @version      0.1
// @description  Adds a 'fullscreen' button to GitLab diffs.
// @match        http://*
// @require      http://ajax.googleapis.com/ajax/libs/jquery/1/jquery.min.js
// @grant        none
// ==/UserScript==
/**
 * Be sure to change the @match param above to suit your needs.
 * This script requires the Tampermonkey extension for Chrome. You can download it here: 
 * 
 * https://chrome.google.com/webstore/detail/tampermonkey/dhdgffkkebhmkfjojejmpbldmpobfkfo?hl=en
 */
function make_button() {
    return $('<button/>').text('Fullscreen').addClass('btn btn-small btn-fullscreen').css('background-color', '#fff200');
}

function toggle_fullscreen(div) {
    if (div.data('fullscreen')) {
        style = {
            'width': '95%',
            'margin-bottom': '2em',
            'left': '2.5%',
            'position': 'absolute',
            'box-shadow': '1em 1em 1em #ccc',
            'z-index': 9999
        };
        div.data('fullscreen', 0);
    } else {
        style = {
            'width': '100%',
            'margin-bottom': '1em',
            'left': 'initial',
            'position': 'initial',
            'box-shadow': 'none'
        };
        div.data('fullscreen', 1);
    }
    div.css(style);
}

$(function() {
    $('.diff-file').each(function() {
        $(this).find('.diff-header').prepend(make_button()); 
    });
    
    $('.btn-fullscreen').on('click', function() {
        var diff = $(this).parents('.diff-file');
        toggle_fullscreen(diff);
    });
});