Regex not successful for cases

[schmorrison]

I am attempting to include this plugin with my build pipeline. Currently I am only passing the following types of image elements:

<source srcset="/path/to/example-image-100x100.png"> and
<img srcset="/path/to/example-image.png">

In trying to figure out the problem, it seems like the Regex doesn't accept either of these cases. I edited the Regex to be much more relaxed, eg. ([a-z\-_0-9\/\:\.]*\.(jpg|png)) which does seem to function for my case, however I am only extracting from HTML. I am not sure how that might break usage in CSS (or even for edge cases in HTML).

I didn't submit a PR for this for the reasons mentioned above.