Fix bug with css build not properly prefixing things for Firefox

Author: DaneEveritt

package.json

@@ -78,11 +78,11 @@
         "glob-all": "^3.1.0",
         "html-webpack-plugin": "^3.2.0",
         "mini-css-extract-plugin": "^0.8.0",
-        "postcss": "^6.0.21",
-        "postcss-import": "^11.1.0",
+        "postcss": "^7.0.21",
+        "postcss-import": "^12.0.1",
         "postcss-loader": "^3.0.0",
-        "postcss-preset-env": "^3.4.0",
-        "precss": "^3.1.2",
+        "postcss-preset-env": "^6.7.0",
+        "precss": "^4.0.0",
         "purgecss-webpack-plugin": "^1.1.0",
         "resolve-url-loader": "^3.0.0",
         "source-map-loader": "^0.2.4",
@@ -105,6 +105,9 @@
         "serve": "yarn run clean && PUBLIC_PATH=https://pterodactyl.test:8080 NODE_ENV=development webpack-dev-server --host 0.0.0.0 --hot --https --key /etc/ssl/private/pterodactyl.test-key.pem --cert /etc/ssl/private/pterodactyl.test.pem"
     },
     "browserslist": [
-        "defaults"
+        "> 0.5%",
+        "last 2 versions",
+        "firefox esr",
+        "not dead"
     ]
 }