feat: Headings Anchoring, Text Highlighting

[nksazonov]

Hi!

Thanks for implementing an incredibly useful tool for viewing EIPs.
Apart from an already extensive set of features, I think that eiptools can benefit from additional set of functionality:

Anchor Links (Fragment Identifiers)

Deep-linking to specific sections of an EIP—like “Motivation,” “Specification,” or “Rationale”—is essential for efficient collaboration. When reviewers, implementers, or community members share a link that jumps straight to the precise heading they’re discussing, it cuts out needless scrolling and context-switching. This reduces friction during code reviews, editorial discussions, and in-person presentations, ensuring everyone lands on the exact section under debate and stays focused on the relevant content.

Text Fragments (Scroll-to-Text Highlighting)

Being able to highlight and share an exact phrase—be it a critical sentence about gas costs or a subtle nuance in wording—elevates clarity in high-stakes protocol discussions. Rather than pointing someone to an entire section and asking them to find the line, text fragments zero in on the verbatim text that matters. This precision empowers faster feedback, prevents misinterpretation of adjacent text, and fosters more productive discourse when refining EIPs.

I think that these features will improve the usability of the platform.