[FEATURE] move offline cache to a dot-folder

install.sh

@@ -61,7 +61,7 @@ npm install yarn
 
 # offline mirror
 echo -e "\033[0;34mCreate offline mirror for node deps\033[0m";
-node_modules/yarn/bin/yarn config set yarn-offline-mirror ./sgc-packages-offline-cache
+node_modules/yarn/bin/yarn config set yarn-offline-mirror ./.sgc-packages-offline-cache
 node_modules/yarn/bin/yarn config set yarn-offline-mirror-pruning true
 
 node_modules/yarn/bin/yarn install