chore: relicense @unom/style under MIT

Relicense from GPL-3.0-or-later to MIT and add the LICENSE file. A dependency audit
confirmed no copyleft (GPL/LGPL/AGPL) deps and no vendored copyleft source, so
the relicense is valid. Patch version bumped for the registry.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

package.json

@@ -1,6 +1,6 @@
 {
 	"name": "@unom/style",
-	"version": "0.4.4",
+	"version": "0.4.5",
 	"description": "The official unom-style library",
 	"type": "module",
 	"files": [
@@ -25,7 +25,7 @@
 	},
 	"keywords": [],
 	"author": "enricobuehler",
-	"license": "GPL-3.0-or-later",
+	"license": "MIT",
 	"devDependencies": {
 		"@biomejs/biome": "^2.3.13",
 		"@types/node": "^25.2.0",