feat: brew and apt packages

script/install.d/70-cca.sh

@@ -0,0 +1,12 @@
+#!/usr/bin/env bash
+
+# -----------------------------------------------------------------------------
+# Description:
+#   (macOS only) Install Colour Contrast Analyser (CCA).
+#
+
+if [[ "$OSTYPE" == "darwin"* ]]; then
+    if ! command -v cca &> /dev/null; then
+        brew install --cask colour-contrast-analyser
+    fi
+fi