Bump postcss from 8.4.20 to 8.4.31 in /demo/vue (#665)

demo/vue/yarn.lock

@@ -1531,10 +1531,10 @@ muggle-string@^0.1.0:
   resolved "https://registry.yarnpkg.com/muggle-string/-/muggle-string-0.1.0.tgz#1fda8a281c8b27bb8b70466dbc9f27586a8baa6c"
   integrity sha512-Tr1knR3d2mKvvWthlk7202rywKbiOm4rVFLsfAaSIhJ6dt9o47W4S+JMtWhd/PW9Wrdew2/S2fSvhz3E2gkfEg==
 
-nanoid@^3.3.4:
-  version "3.3.4"
-  resolved "https://registry.yarnpkg.com/nanoid/-/nanoid-3.3.4.tgz#730b67e3cd09e2deacf03c027c81c9d9dbc5e8ab"
-  integrity sha512-MqBkQh/OHTS2egovRtLk45wEyNXwF+cokD+1YPf9u5VfJiRdAiRwB2froX5Co9Rh20xs4siNPm8naNotSD6RBw==
+nanoid@^3.3.6:
+  version "3.3.6"
+  resolved "https://registry.yarnpkg.com/nanoid/-/nanoid-3.3.6.tgz#443380c856d6e9f9824267d960b4236ad583ea4c"
+  integrity sha512-BGcqMMJuToF7i1rt+2PWSNVnWIkGCU78jBG3RxO/bZlnZPK2Cmi2QaffxGO/2RvWi9sL+FAiRiXMgsyxQ1DIDA==
 
 natural-compare-lite@^1.4.0:
   version "1.4.0"
@@ -1717,11 +1717,11 @@ postcss-selector-parser@^6.0.9:
     util-deprecate "^1.0.2"
 
 postcss@^8.1.10, postcss@^8.4.18:
-  version "8.4.20"
-  resolved "https://registry.yarnpkg.com/postcss/-/postcss-8.4.20.tgz#64c52f509644cecad8567e949f4081d98349dc56"
-  integrity sha512-6Q04AXR1212bXr5fh03u8aAwbLxAQNGQ/Q1LNa0VfOI06ZAlhPHtQvE4OIdpj4kLThXilalPnmDSOD65DcHt+g==
+  version "8.4.31"
+  resolved "https://registry.yarnpkg.com/postcss/-/postcss-8.4.31.tgz#92b451050a9f914da6755af352bdc0192508656d"
+  integrity sha512-PS08Iboia9mts/2ygV3eLpY5ghnUcfLV/EXTOW1E2qYxJKGGBUtNjN76FYHnMs36RmARn41bC0AZmn+rR0OVpQ==
   dependencies:
-    nanoid "^3.3.4"
+    nanoid "^3.3.6"
     picocolors "^1.0.0"
     source-map-js "^1.0.2"