Update OpenLess Homebrew cask from 1.2.23 to 1.3.4 (latest stable
release v1.3.4-tauri, published 2026-05-22). SHA256 checksums for
both aarch64 and x64 DMGs verified by local download.
Adds Casks/openless.rb + update-cask.yml workflow + README install docs. Closes#254#5.
Note: Formula/openless.rb known to fail in Homebrew sandbox (per author); will be removed in follow-up. Cask version will be bumped to current 1.2.23 in same follow-up.