Merge branch 'develop' into css-variables

# Conflicts:
#	demo/dist/demo.css
#	demo/dist/demo.min.js.map
#	demo/index.html
#	dist/plyr.css
#	dist/plyr.min.js.map
#	dist/plyr.min.mjs.map
#	dist/plyr.polyfilled.min.js.map
#	dist/plyr.polyfilled.min.mjs.map
#	gulpfile.js
#	src/sass/base.scss
#	src/sass/components/control.scss
#	src/sass/settings/colors.scss
#	src/sass/settings/controls.scss

src/sass/lib/css-vars.scss

@@ -27,7 +27,7 @@ $css-vars-use-native: false !default;
 //
 // E.G.:
 // color: var(--main-color);
-// background: var(--main-bg, green);
+// background: var(--main-background, green);
 ///
 @function var($args...) {
     // CHECK PARAMS