added pkg-config

Author: dmalan

Dockerfile

@@ -1,6 +1,6 @@
 FROM cs50/cli
 
-RUN sudo apt update && sudo apt install --yes libmysqlclient-dev pgloader postgresql
+RUN sudo apt update && sudo apt install --yes libmysqlclient-dev pgloader pkg-config postgresql
 RUN sudo pip3 install mysqlclient psycopg2-binary
 
 WORKDIR /mnt