Rename actions folder as scripts

It's clearer this way.

.github/scripts/install_deps.sh

@@ -0,0 +1,21 @@
+#!/bin/bash
+set -e
+
+case "${1%-*}" in
+	ubuntu)
+		sudo apt-get -qq update
+		sudo apt-get install -yq bison libpng-dev pkg-config
+		;;
+	macos)
+		brew install bison libpng pkg-config md5sha1sum
+		# For the version check below exclusively, re-do this before building
+		export PATH="/usr/local/opt/bison/bin:$PATH"
+		;;
+	*)
+		echo "WARNING: Cannot install deps for OS '$1'"
+		;;
+esac
+
+bison --version
+make --version
+cmake --version