docs: document URL.parse requirement and polyfill for Chrome <126 and Safari <18

[mikev-lab]

Summary

Modern versions of pdfjs-dist utilize the WHATWG static method URL.parse() (Baseline 2024). While the browser support section currently notes Chrome 125 as a minimum, URL.parse() was only introduced in Chrome 126 and Safari 18.

In environments running Chrome <126 (e.g. Chrome 122–125), Safari <18, or older embedded mobile webviews, this causes an unhandled TypeError: URL.parse is not a function during viewer initialization.

Changes

• Added a ##### Polyfilling URL.parse subsection under Compatibility -> Browser support.
• Documented the runtime versions where URL.parse is natively available (Chrome 126+, Safari 18+, Node 22.1.0+).
• Provided the standard WHATWG-compliant non-throwing polyfill snippet for developers needing to support those environments.

[wojtekmaj]

Thank you!