PSA: Upcoming Fix for data: URL MIME Type Parameter Preservation

[Helmut Januschka]

Hello,

this is an advance notice about an upcoming change that fixes how MIME type parameters within `data:` URLs are parsed and preserved.

This CL is a correctness fix addressing Web Platform Test (WPT) compliance. It updates the data: URL parser  to ensure that all MIME type parameters (e.g., the charset=... ) are fully preserved and correctly associated with the request's MIME type. Previously, these parameters could be incorrectly dropped or handled, leading to compliance failures. This change ensures accurate parsing of data: URLs according to the standards.

cheers