Add initial form support

Draft code to find & prefill forms.

Add links for navigating through the XML/HTML tree.

Show syntax-highlighted start tags for elements in HTML UI.

Add support for querying elements by CSS selector.

Uses a fork of the  hackage, altered to use  as a lexer.

Parse web (or Gemini) pages & extract title.

Allow navigating (tab) history.

Refactoring, allowing reading which URL was loaded.

Allow loading webpage, commit missing files.