Update dependency postcss to v8.4.18

package.json

@@ -56,7 +56,7 @@
         "gulp-util": "3.0.8",
         "gulp-watch": "5.0.1",
         "gulp-zip": "5.1.0",
-        "postcss": "8.4.17",
+        "postcss": "8.4.18",
         "postcss-color-function": "4.1.0",
         "postcss-custom-properties": "11.0.0",
         "postcss-easy-import": "3.0.0"

yarn.lock

@@ -4017,10 +4017,10 @@ postcss-values-parser@^4.0.0:
     is-url-superb "^4.0.0"
     postcss "^7.0.5"
 
-[email protected].17:
-  version "8.4.17"
-  resolved "https://registry.yarnpkg.com/postcss/-/postcss-8.4.17.tgz#f87863ec7cd353f81f7ab2dec5d67d861bbb1be5"
-  integrity sha512-UNxNOLQydcOFi41yHNMcKRZ39NeXlr8AxGuZJsdub8vIb12fHzcq37DTU/QtbI6WLxNg2gF9Z+8qtRwTj1UI1Q==
+[email protected].18:
+  version "8.4.18"
+  resolved "https://registry.yarnpkg.com/postcss/-/postcss-8.4.18.tgz#6d50046ea7d3d66a85e0e782074e7203bc7fbca2"
+  integrity sha512-Wi8mWhncLJm11GATDaQKobXSNEYGUHeQLiQqDFG1qQ5UTDPTEvKw0Xt5NsTpktGTwLps3ByrWsBrG0rB8YQ9oA==
   dependencies:
     nanoid "^3.3.4"
     picocolors "^1.0.0"