style: improve SCSS style

.stylelintrc.json

@@ -1,3 +1,22 @@
 {
-  "extends": "stylelint-config-standard-scss"
+  "extends": "stylelint-config-standard-scss",
+  "rules": {
+    "no-descending-specificity": null,
+    "shorthand-property-no-redundant-values": null,
+    "at-rule-no-vendor-prefix": null,
+    "property-no-vendor-prefix": null,
+    "selector-no-vendor-prefix": null,
+    "value-no-vendor-prefix": null,
+    "color-function-notation": "legacy",
+    "alpha-value-notation": "number",
+    "selector-not-notation": "simple",
+    "color-hex-length": "long",
+    "declaration-block-single-line-max-declarations": 3,
+    "font-family-no-missing-generic-family-keyword": [
+      true,
+      {
+        "ignoreFontFamilies": ["Font Awesome 5 Free"]
+      }
+    ]
+  }
 }