fix: package.json & yarn.lock to reduce vulnerabilities

The following vulnerabilities are fixed with an upgrade:
- https://snyk.io/vuln/SNYK-JS-POSTCSS-5926692

package.json

@@ -77,6 +77,6 @@
 	"dependencies": {
 		"marked": "^4.0.10",
 		"nanoid": "^3.1.31",
-		"postcss": "^8.2.13"
+		"postcss": "^8.4.31"
 	}
 }

yarn.lock

@@ -4823,7 +4823,7 @@ nan@^2.12.1:
   version "2.17.0"
   resolved "https://registry.yarnpkg.com/nan/-/nan-2.17.0.tgz#c0150a2368a182f033e9aa5195ec76ea41a199cb"
 
-nanoid@^3.1.31, nanoid@^3.3.6:
+nanoid@^3.1.31, nanoid@^3.3.6, nanoid@^3.3.7:
   version "3.3.6"
   resolved "https://registry.yarnpkg.com/nanoid/-/nanoid-3.3.6.tgz#443380c856d6e9f9824267d960b4236ad583ea4c"
 
@@ -5177,6 +5177,11 @@ picocolors@^1.0.0:
   version "1.0.0"
   resolved "https://registry.yarnpkg.com/picocolors/-/picocolors-1.0.0.tgz#cb5bdc74ff3f51892236eaf79d68bc44564ab81c"
 
+picocolors@^1.0.1:
+  version "1.0.1"
+  resolved "https://registry.yarnpkg.com/picocolors/-/picocolors-1.0.1.tgz#a8ad579b571952f0e5d25892de5445bcfe25aaa1"
+  integrity sha512-anP1Z8qwhkbmu7MFP5iTt+wQKXgwzf7zTyGlcdzabySa9vd0Xt392U0rVmz9poOaBj0uHJKyyo9/upk0HrEQew==
+
 picomatch@^2.0.4, picomatch@^2.2.3, picomatch@^2.3.1:
   version "2.3.1"
   resolved "https://registry.yarnpkg.com/picomatch/-/picomatch-2.3.1.tgz#3ba3833733646d9d3e4995946c1365a67fb07a42"
@@ -5252,6 +5257,15 @@ postcss@^7.0.16, postcss@^8.1.7, postcss@^8.2.13, postcss@^8.4.23:
     picocolors "^1.0.0"
     source-map-js "^1.0.2"
 
+postcss@^8.4.31:
+  version "8.4.41"
+  resolved "https://registry.yarnpkg.com/postcss/-/postcss-8.4.41.tgz#d6104d3ba272d882fe18fc07d15dc2da62fa2681"
+  integrity sha512-TesUflQ0WKZqAvg52PWL6kHgLKP6xB6heTOdoYM0Wt2UHyxNa4K25EZZMgKns3BH1RLVbZCREPpLY0rhnNoHVQ==
+  dependencies:
+    nanoid "^3.3.7"
+    picocolors "^1.0.1"
+    source-map-js "^1.2.0"
+
 precinct@^8.1.0:
   version "8.3.1"
   resolved "https://registry.yarnpkg.com/precinct/-/precinct-8.3.1.tgz#94b99b623df144eed1ce40e0801c86078466f0dc"
@@ -5759,6 +5773,11 @@ source-map-js@^1.0.2:
   version "1.0.2"
   resolved "https://registry.yarnpkg.com/source-map-js/-/source-map-js-1.0.2.tgz#adbc361d9c62df380125e7f161f71c826f1e490c"
 
+source-map-js@^1.2.0:
+  version "1.2.0"
+  resolved "https://registry.yarnpkg.com/source-map-js/-/source-map-js-1.2.0.tgz#16b809c162517b5b8c3e7dcd315a2a5c2612b2af"
+  integrity sha512-itJW8lvSA0TXEphiRoawsCksnlf8SyvmFzIhltqAHluXd88pkCd+cXJVHTDwdCr0IzwptSm035IHQktUu1QUMg==
+
 source-map-resolve@^0.5.0:
   version "0.5.3"
   resolved "https://registry.yarnpkg.com/source-map-resolve/-/source-map-resolve-0.5.3.tgz#190866bece7553e1f8f267a2ee82c606b5509a1a"