Adjust build_docs.sh for invocation from an external directory (PR #97)

Author: joaquintides

doc/build_docs.sh

@@ -18,6 +18,9 @@ else
     PLAYBOOK=$1
 fi
 
+SCRIPT_DIR=$( dirname -- "${BASH_SOURCE[0]}" )
+cd "$SCRIPT_DIR"
+
 echo "Installing npm dependencies..."
 npm ci