Add a regex-based parser (parsers/hubl.ts) for HubL (HubSpot CMS templating).
No tree-sitter grammar exists for HubL, so macros, blocks, and include/extends/
import/from paths are extracted with targeted regexes. Plain HTML files with no
HubL tags yield zero symbols — same as before. Dispatch added in parser.ts for
.html/.hubl; both extensions added to RESOLVE_EXTS in extract.ts so relative
include paths resolve to local graph nodes. Tests in tests/hubl.test.ts cover
macro/block extraction, import-edge resolution, whitespace-control tags, and
plain-HTML no-op behaviour.