fix(madara): properly parse srcset with image descriptors (w/x suffixes)

[IMXEren]

Refactored getSrcSetImage() to correctly handle comma-separated srcset entries with width (w) and pixel-density (x) descriptors. Previously the method used to compare URLs lexicographically, which breaks on srcset="link-34x68.jpg 34w, link-330x700.jpg 330w" and chooses link-34x68.jpg.

Adds IMAGE_DESCRIPTOR_REGEX companion constant and prefers highest-resolution images by descriptor value, falling back to lexicographical URL comparison when no descriptors are present.

Checklist:

• Updated versionCode value in build.gradle.kts
• Updated baseVersionCode in build.gradle.kts (if updated multisrc theme code)
• Referenced all related issues in the PR body (e.g. "Closes #xyz")
• Set the contentWarning configuration in build.gradle.kts appropriately
• Have not changed source names
• Have explicitly kept the id if a source's name or language were changed
• Have tested the modifications by compiling and running the extension through Android Studio
• Have removed web_hi_res_512.png when adding a new extension
• This PR is AI-assisted, I have reviewed the changes manually and confirmed they are not slop