Update dart-sass (#650)

Author: jarrodmillman

doc/netlify.toml

@@ -1,7 +1,7 @@
 [build.environment]
   PYTHON_VERSION = "3.8" # netlify currently only support 2.7 and 3.8
   HUGO_VERSION = "0.139.0"
-  DART_SASS_VERSION = "1.77.5"
+  DART_SASS_VERSION = "1.81.0"
   DART_SASS_URL = "https://github.com/sass/dart-sass/releases/download/"
 
 [context.production.environment]