fix: adding yarn silent

Author: carlosala

lib/install.sh

@@ -5,7 +5,7 @@ set -e
 LIBDIR=$(cd $(dirname $0); pwd)
 
 if [ -x "$(command -v yarn)" ]; then
-  yarn --cwd "${LIBDIR}"
+  yarn -s --cwd "${LIBDIR}"
   ln -fs "${LIBDIR}/node_modules/.bin/lehre" "${LIBDIR}/lehre"
 elif [ -x "$(command -v npm)" ]; then
   cd "$LIBDIR"