adding list of web safe fonts link closes #1606

Author: Lauren McCarthy

src/typography/loading_displaying.js

@@ -87,7 +87,8 @@ p5.prototype.text = function(str, x, y, maxWidth, maxHeight) {
  *
  * @method textFont
  * @param {Object|String} f a font loaded via loadFont(), or a String
- *  representing a browser-based default font.
+ * representing a <a href="https://mzl.la/2dOw8WD">web safe font</a> (a font
+ * that is generally available across all systems).
  * @return {Object} this
  * @example
  * <div>