HTML 'Class not found' errors when using CDN stylesheet

### Apache NetBeans version

Apache NetBeans 16

### What happened

When adding bootstrap (or other frameworks) in a html/php project using a CDN directly, the remote file isn't parsed/cached so any CSS class used within the html page generates a "Class ... not found" error/warning light bulb.

Large projects that use CDNs thus have hundreds of warning light bulbs unnecessarily.

### How to reproduce

Create a basic HTML or PHP Project.

Put this code in the index.html/index.php file

```HTML

```

Lines 6, 7 & 8 shows errors/warnings


### Did this work correctly in an earlier version?

No / Don't know

### Operating System

Windows 10

### JDK

19

### Apache NetBeans packaging

Apache NetBeans provided installer

### Anything else

_No response_

### Are you willing to submit a pull request?

No

### Code of Conduct

Yes

Reproduce the problem in index.html or index.php with the Bootstrap CDN stylesheet and inspect the “Class ... not found” diagnostics on the referenced lines. Trace the NetBeans HTML/CSS analysis responsible for remote stylesheets; done means CDN-defined classes no longer produce spurious warnings while local class diagnostics remain.

Written by the indexing model from the issue text.