Add note regarding font-size-dependent font measurement

src/render/measure-text.js

@@ -3,7 +3,6 @@
 const memoizee = require("memoizee");
 
 const setTextStyles = require("./set-text-styles");
-//const measureFont = memoizee(require("./measure-font"));
 const measureFont = memoizee(require("measure-font"));
 
 module.exports = function measureText(text, options) {
@@ -12,6 +11,7 @@ module.exports = function measureText(text, options) {
 
 	setTextStyles(context, options);
 
+	// FIXME: Allow for more accurate measurement
 	let fontMeasurements = measureFont(options.fontFamily, {fontSize: 40});
 
 	return Object.assign(context.measureText(text), {