Merge branch 'develop' into css-variables

# Conflicts:
#	.eslintrc
#	demo/dist/demo.css
#	demo/dist/demo.js
#	demo/dist/demo.min.js
#	demo/dist/demo.min.js.map
#	dist/plyr.css
#	dist/plyr.js
#	dist/plyr.min.js
#	dist/plyr.min.js.map
#	dist/plyr.min.mjs
#	dist/plyr.min.mjs.map
#	dist/plyr.mjs
#	dist/plyr.polyfilled.js
#	dist/plyr.polyfilled.min.js
#	dist/plyr.polyfilled.min.js.map
#	dist/plyr.polyfilled.min.mjs
#	dist/plyr.polyfilled.min.mjs.map
#	dist/plyr.polyfilled.mjs
#	gulpfile.js
#	package.json

gulpfile.js

@@ -6,26 +6,30 @@
 
 const path = require('path');
 const gulp = require('gulp');
-
+// ------------------------------------
 // JavaScript
+// ------------------------------------
 const terser = require('gulp-terser');
 const rollup = require('gulp-better-rollup');
 const babel = require('rollup-plugin-babel');
 const commonjs = require('rollup-plugin-commonjs');
 const resolve = require('rollup-plugin-node-resolve');
-
+// ------------------------------------
 // CSS
+// ------------------------------------
 const sass = require('gulp-sass');
 const clean = require('gulp-clean-css');
 const prefix = require('gulp-autoprefixer');
 const postcss = require('gulp-postcss');
 const customprops = require('postcss-custom-properties');
-
+// ------------------------------------
 // Images
+// ------------------------------------
 const svgstore = require('gulp-svgstore');
 const imagemin = require('gulp-imagemin');
-
+// ------------------------------------
 // Utils
+// ------------------------------------
 const del = require('del');
 const filter = require('gulp-filter');
 const header = require('gulp-header');
@@ -39,18 +43,22 @@ const plumber = require('gulp-plumber');
 const size = require('gulp-size');
 const sourcemaps = require('gulp-sourcemaps');
 const through = require('through2');
-
+// ------------------------------------
 // Deployment
+// ------------------------------------
 const aws = require('aws-sdk');
 const publish = require('gulp-awspublish');
 const FastlyPurge = require('fastly-purge');
-
+// ------------------------------------
+// Configs
+// ------------------------------------
 const pkg = require('./package.json');
 const build = require('./build.json');
 const deploy = require('./deploy.json');
-
+// ------------------------------------
+// Info from package
+// ------------------------------------
 const { browserslist: browsers, version } = pkg;
-
 const minSuffix = '.min';
 
 // Get AWS config
@@ -151,6 +159,7 @@ Object.entries(build.js).forEach(([filename, entry]) => {
                                             {
                                                 // debug: true,
                                                 useBuiltIns: polyfill ? 'usage' : false,
+                                                corejs: polyfill ? 3 : undefined,
                                             },
                                         ],
                                     ],