formula: add htacg/tidy-html5

[MeteorsLiu]

Translate the pinned Conan Center tidy-html5 5.8.0 recipe into an idiomatic LLAR Formula.

• Builds and installs the upstream CMake project through LLAR's CMake helper with the verified Conan options and pinned PDB patch.
• Publishes relocatable tidy.pc metadata and verifies the Conan consumer against the complete pkg-config lookup on fresh and cache-hit builds.
• Uses 5.8.0 as the earliest compatible fromVer; 5.6.0 was rejected because its installed static library is libtidys.a rather than libtidy.a.

Closes #246

[fennoai]

Reviewed the complete tidy-html5 Formula unit, including version selection, option filtering, CMake configuration and patching, install cleanup, pkg-config metadata, licensing, and the consumer test. The packaging contract is coherent and I found no actionable correctness or compatibility regressions in the changed code.

Verification performed locally:

• llar test --verbose ./htacg/tidy-html5@5.8.0 --os linux --arch amd64
• llar test --verbose ./htacg/tidy-html5 --os linux --arch amd64
• llar test --verbose ./htacg/tidy-html5 --os linux --arch amd64 --option shared=ON