fix: inconsistent naming style

Always use two dashes after prefix.

Author: pau4o

css/simple-css-switch.css

@@ -7,10 +7,10 @@
     padding: 1em;
     border: .2em inset #a6a659;
 }
-.s-css-s-button:focus {
+.s-css-s--button:focus {
     outline: 0 none;
 }
-.s-css-s-button {
+.s-css-s--button {
     display: block;
     width: 100%;
     margin: .2em;
@@ -27,15 +27,15 @@
     position: relative;
     left: -.5em;
 }
-.s-css-s-main-css {
+.s-css-s--main-css {
     color: #eee;
     background-color: #2c2c2c;
 }
-.s-css-s-red-css {
+.s-css-s--red-css {
     color: #dcd;
     background-color: #2e0505;
 }
-.s-css-s-green-css {
+.s-css-s--green-css {
     color: #ddd;
     background-color: #122112;
 }

js/simple-css-switch.js

@@ -5,10 +5,10 @@ function simpleCssSwitch() {
         document.querySelectorAll('.s-css-s--style')
     );
     stylesAvailable.forEach(function(style, idx) {
-        var cssFileAsClass = 's-css-s-' + style.href.split('/').pop().replace('.', '-');
+        var cssFileAsClass = 's-css-s--' + style.href.split('/').pop().replace('.', '-');
         var styleOptionButton = document.createElement('button');
         styleOptionButton.setAttribute('title', style.title);
-        styleOptionButton.classList.add('s-css-s-button', cssFileAsClass);
+        styleOptionButton.classList.add('s-css-s--button', cssFileAsClass);
         styleOptionButton.innerText = idx;
         styleOptionButton.addEventListener(
             'click', function(e) {