SipLoader cannot distinguish between data URIs and real URLs in CSS files

[Web-Distortion]

As shown below, the regular expression for URL matching cannot filter out data URIs (e.g., url(data:image/png;base64,...)).

SipLoader.github.io/scheduler/rewrite_css_file.py

Line 17 in f831cde

pattern = r"url\([\"']?(.*?)[\"']?\)"

In fact, many CSS files have data URIs, which can confuse SipLoader during the rewriting phase and make the corresponding URI resources unable to be loaded.