chore: move postcss to peerDependencies (#459)

BREAKING CHANGE: `postcss` was moved to `peerDependencies`

Author: evilebottnawi

.github/workflows/nodejs.yml

@@ -43,8 +43,8 @@ jobs:
       - name: Lint
         run: npm run lint
 
-      # - name: Security audit
-      #  run: npm run security
+      - name: Security audit
+        run: npm run security
 
       - name: Check commit message
         uses: wagoid/commitlint-github-action@v1

README.md

@@ -26,7 +26,7 @@
 <h2 align="center">Install</h2>
 
 ```bash
-npm i -D postcss-loader
+npm i -D postcss-loader postcss
 ```
 
 <h2 align="center">Usage</h2>