devel/rgx: Add new port
Rgx is a regex debugger for the terminal — step-through execution, 3 engines,
code generation, and live stream filtering.
rgx is useful if you:
- Work on remote servers where opening a browser isn't practical — SSH, containers, air-gapped environments.
- Want to pipe regex results into other commands (echo "log" | rgx -p '\d+' | sort) — regex101 can't do this.
- Need engine-specific behavior — check whether a pattern works in Rust's regex crate vs. PCRE2 without guessing.
- Prefer staying in the terminal and find the context switch to a browser disruptive.