chore: Stylelint

add Stylelint

.gitignore

@@ -19,3 +19,4 @@ nbproject
 _site
 .jekyll-metadata
 .sass-cache
+node_modules

.prettierignore

@@ -0,0 +1,4 @@
+_site
+.jekyll-metadata
+.sass-cache
+node_modules

.prettierrc

@@ -0,0 +1,5 @@
+{
+  "printWidth": 120,
+  "singleQuote": true,
+  "trailingComma": "all"
+}

.stylelintignore

@@ -0,0 +1,4 @@
+_site
+.jekyll-metadata
+.sass-cache
+node_modules

.stylelintrc

@@ -0,0 +1,12 @@
+{
+  "extends": [
+    "stylelint-config-prettier",
+    "stylelint-config-standard"
+  ],
+  "plugins": [
+    "stylelint-order"
+  ],
+  "rules": {
+    "order/properties-alphabetical-order": true
+  }
+}

package.json

@@ -0,0 +1,32 @@
+{
+  "name": "search-engine-optimization",
+  "version": "1.0.0",
+  "description": "[![Awesome](https://cdn.rawgit.com/sindresorhus/awesome/d7305f38d29fed78fa85652e3a63e154dd8e8829/media/badge.svg)](https://github.com/sindresorhus/awesome) [![Join the chat at https://gitter.im/marcobiedermann/search-engine-optimization](https://badges.gitter.im/Join%20Chat.svg)](https://gitter.im/marcobiedermann/search-engine-optimization)",
+  "main": "index.js",
+  "scripts": {
+    "fix:css": "npm run lint:css -- --fix",
+    "fix": "npm run fix:css",
+    "format": "prettier --write '**/*.{css,html,js,json,md,scss,yml,yaml}'",
+    "lint:css": "stylelint '**/*.{css,scss}'",
+    "lint": "npm run lint:css",
+    "test": "npm run lint"
+  },
+  "repository": {
+    "type": "git",
+    "url": "git+https://github.com/marcobiedermann/search-engine-optimization.git"
+  },
+  "keywords": [],
+  "author": "",
+  "license": "ISC",
+  "bugs": {
+    "url": "https://github.com/marcobiedermann/search-engine-optimization/issues"
+  },
+  "homepage": "https://github.com/marcobiedermann/search-engine-optimization#readme",
+  "devDependencies": {
+    "prettier": "^1.18.2",
+    "stylelint": "^10.1.0",
+    "stylelint-config-prettier": "^5.2.0",
+    "stylelint-config-standard": "^18.3.0",
+    "stylelint-order": "^3.0.0"
+  }
+}