chore: rxjs as optional peer dependency

So that e.g. other eslint config packages can pull in this plugin without getting a warning about needing rxjs.

Author: JasonWeinzierl

package.json

@@ -65,6 +65,11 @@
     "rxjs": ">=7.0.0",
     "typescript": ">=4.7.4"
   },
+  "peerDependenciesMeta": {
+    "rxjs": {
+      "optional": true
+    }
+  },
   "devDependencies": {
     "@eslint/js": "^9.14.0",
     "@stylistic/eslint-plugin": "^2.10.1",