fix(axe): dark header contrast improvement

themes/hello-world/go.mod

@@ -2,4 +2,4 @@ module github.com/wowchemy/wowchemy-hugo-modules/themes/hello-world
 
 go 1.15
 
-require github.com/wowchemy/wowchemy-hugo-modules/wowchemy v0.0.0-20201107233547-e18ecbbff3a2
+require github.com/wowchemy/wowchemy-hugo-modules/wowchemy latest

wowchemy/assets/scss/wowchemy/_dark.scss

@@ -29,7 +29,7 @@ body.dark,
 .dark h4,
 .dark h5,
 .dark h6 {
-  color: rgb(152, 166, 173);
+  color: #fff;
 }
 
 .dark pre,