Move postcss to peerDependencies (#273)

Author: XhmikosR

README.md

@@ -8,7 +8,7 @@
 Supports `@import` and [`@value ... from`](https://github.com/css-modules/postcss-icss-values).
 
 ```sh
-npm install detective-postcss
+npm install postcss detective-postcss
 ```
 
 It's the CSS (PostCSS dialect) counterpart to [detective](https://github.com/browserify/detective), [detective-amd](https://github.com/dependents/node-detective-amd), [detective-es6](https://github.com/dependents/node-detective-es6), [detective-sass](https://github.com/dependents/node-detective-sass), [detective-scss](https://github.com/dependents/node-detective-scss).

package-lock.json

@@ -22,16 +22,19 @@
   "engines": {
     "node": "^14.0.0 || >=16.0.0"
   },
+  "peerDependencies": {
+    "postcss": "^8.4.38"
+  },
   "dependencies": {
     "is-url": "^1.2.4",
-    "postcss": "^8.4.38",
     "postcss-values-parser": "^6.0.2"
   },
   "devDependencies": {
     "@types/is-url": "^1.2.32",
     "@types/jest": "^29.5.12",
     "jest": "^29.7.0",
     "lint-staged": "^15.2.2",
+    "postcss": "^8.4.38",
     "prettier": "^3.2.5",
     "rimraf": "^3.0.2",
     "ts-jest": "^29.1.2",