doc: add comment explaining why we cd into the parent folder in start.sh

Author: yavuzkaymak

app/start.sh

@@ -1,5 +1,7 @@
 #!/bin/sh
 
+# cd into the parent directory of the script, 
+# so that the script generates virtual environments always in the same path.
 cd "${0%/*}" || exit 1
 
 cd ../