build: bump postcss to a non-vulnerable version (#229)

diff --git a/package-lock.json b/package-lock.json
index e7f107d..49fe044 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -13626,7 +13626,7 @@
         "loader-utils": "^1.1.0",
         "merge-options": "1.0.1",
         "micromatch": "3.1.0",
-        "postcss": "^5.2.17",
+        "postcss": "^7.0.36",
         "postcss-prefix-selector": "^1.6.0",
         "posthtml-rename-id": "^1.0",
         "posthtml-svg-mode": "^1.0.3",
@@ -13789,9 +13789,9 @@
       }
     },
     "node_modules/svg-baker/node_modules/postcss": {
-      "version": "5.2.18",
-      "resolved": "https://registry.npmjs.org/postcss/-/postcss-5.2.18.tgz",
-      "integrity": "sha512-zrUjRRe1bpXKsX1qAJNJjqZViErVuyEkMTRrwu4ud4sbTtIBRmtaYDrHmcGgmrbsW3MHfmtIf+vJumgQn+PrXg==",
+      "version": "7.0.36",
+      "resolved": "https://registry.npmjs.org/postcss/-/postcss-7.0.36.tgz",
+      "integrity": "sha512-BebJSIUMwJHRH0HAQoxN4u1CN86glsrwsW0q7T+/m44eXOUAxSNdHRkNZPYz5vVUbg17hFgOQDE7fZk7li3pZw==",
       "dev": true,
       "dependencies": {
         "chalk": "^1.1.3",
@@ -26176,7 +26176,7 @@
         "loader-utils": "^1.1.0",
         "merge-options": "1.0.1",
         "micromatch": "3.1.0",
-        "postcss": "^5.2.17",
+        "postcss": "^7.0.36",
         "postcss-prefix-selector": "^1.6.0",
         "posthtml-rename-id": "^1.0",
         "posthtml-svg-mode": "^1.0.3",
@@ -26307,9 +26307,9 @@
           }
         },
         "postcss": {
-          "version": "5.2.18",
-          "resolved": "https://registry.npmjs.org/postcss/-/postcss-5.2.18.tgz",
-          "integrity": "sha512-zrUjRRe1bpXKsX1qAJNJjqZViErVuyEkMTRrwu4ud4sbTtIBRmtaYDrHmcGgmrbsW3MHfmtIf+vJumgQn+PrXg==",
+          "version": "7.0.36",
+          "resolved": "https://registry.npmjs.org/postcss/-/postcss-7.0.36.tgz",
+          "integrity": "sha512-BebJSIUMwJHRH0HAQoxN4u1CN86glsrwsW0q7T+/m44eXOUAxSNdHRkNZPYz5vVUbg17hFgOQDE7fZk7li3pZw==",
           "dev": true,
           "requires": {
             "chalk": "^1.1.3",