Add readtime.js widget

This script displays a "read time" on WriteFreely post pages. It appends
the time next to the date on the post.

readtime.js

@@ -0,0 +1,10 @@
+var wpm = 200; // Average reading rate in words per minute (WPM)
+
+var ps = document.querySelectorAll('p');
+var wordCount = 0;
+for (var i=0; i<ps.length; i++) {
+	wordCount += ps[i].innerText.split(/\s+/).length;
+}
+var $time = document.querySelector('#post-body .dt-published');
+$time.style.display = 'inline-block';
+$time.insertAdjacentHTML("afterend", '<span class="dt-published"> &middot; ' + Math.round(wordCount / wpm) + ' min read</span>');