Add new mp3 logos and adjust p3 logos (#22)

* Add new mp3 logos and adjust p3 logos

* Fix typo

dist/index.html

@@ -24,6 +24,7 @@
     .docs-icon { border: 1px solid #fcfcfc; color: inherit; padding: 9px; transition: .2s }
     .docs-icon a:active { display: inline-block; transform: scale(.9) }
     .docs-icon .nrk-grid > * { font-size: 13px; margin: 5px }
+    .docs-icon .nrk-grid > svg { font-size: 10px }
     .docs-icon:hover { background: #141517; color: #fff }
   </style>
 </head>
@@ -45,6 +46,7 @@ <h3>Getting started</h3>
       will be available as <a target="_blank" href="https://css-tricks.com/svg-symbol-good-choice-icons/">svg symbols</a>:
     </p>
     <pre class="prettyprint">&lt;script async src="https://static.nrk.no/core-icons/latest/core-icons.min.js"&gt;&lt;/script&gt;</pre>
+    <p><small><strong>NB:</strong> For sharpest rendering on web, scale icons with <code class="prettyprint">font-size: 10px</code> (or other number divisible with 10).</small></p>
     <h3>Shortcuts</h3>
     <p>
       <a class="nrk-button" target="_top" href="https://github.com/nrkno/core-icons/archive/master.zip"><svg width="15" height="15"><use xlink:href="#nrk-download" /></svg> Download icons</a>