Feature request: custom rule constraint for solder-mask-expansion.

Description

(rule "no mask expansion on vias"
    (constraint solder_mask_expansion (min 0mm))
    (condition "A.type == via"))

KiCad Version

Application: KiCad PCB Editor arm64 on arm64

Version: 7.99.0-2671-ga9bfadd71a-dirty, debug build

Libraries:
	wxWidgets 3.2.2
	FreeType 2.12.1
	HarfBuzz 5.3.1
	FontConfig 2.14.1
	libcurl/8.1.2 (SecureTransport) LibreSSL/3.3.6 zlib/1.2.11 nghttp2/1.45.1

Platform: macOS Monterey Version 12.6.8 (Build 21G725), 64 bit, Little endian, wxMac

Build Info:
	Date: Sep  7 2023 18:07:24
	wxWidgets: 3.2.2 (wchar_t,wx containers)
	Boost: 1.80.0
	OCC: 7.6.3
	Curl: 7.79.1
	ngspice: 38
	Compiler: Clang 13.1.6 with C++ ABI 1002

Build settings:
	KICAD_STDLIB_DEBUG=OFF
	KICAD_STDLIB_LIGHT_DEBUG=OFF
	KICAD_SANITIZE_ADDRESS=OFF
	KICAD_SANITIZE_THREADS=OFF