fix: factor hueRegexp out of the loop

lib/dom-styles-reader.js

@@ -134,6 +134,7 @@ export default class DOMStylesReader {
 
 const dotRegexp = /\.+/g
 const rgbExtractRegexp = /rgb(a?)\((\d+), (\d+), (\d+)(, (\d+(\.\d+)?))?\)/
+const hueRegexp = /hue-rotate\((\d+)deg\)/
 
 /**
  * Computes the output color of `value` with a rotated hue defined
@@ -148,7 +149,7 @@ function rotateHue (value, filter) {
   const match = value.match(rgbExtractRegexp)
   let [, , r, g, b, , a] = match
 
-  let [, hue] = filter.match(/hue-rotate\((\d+)deg\)/)
+  let [, hue] = filter.match(hueRegexp)
 
   ;[r, g, b, a, hue] = [r, g, b, a, hue].map(Number)
   ;[r, g, b] = rotate(r, g, b, hue)