feat: create empty config file if one does not exist

This explicitly informs users that the file needs to be updated.
Otherwise, users end up with empty variables for project name, author
and so on.

calliope.sh

@@ -31,6 +31,15 @@ default_commit_message="Add new entry"
 if [ -f .callioperc ]
 then
     source .callioperc
+else
+    echo "No .callioperc file found. Creating file with empty fields."
+    echo "Please fill in the necessary information."
+    echo "It will be used in subsequent runs."
+    echo "ProjectName=\"\"" > .callioperc
+    echo "author=\"\"" >> .callioperc
+    echo "bibsrc=\"\"" >> .callioperc
+    echo "encryptionId=\"\"" >> .callioperc
+    exit 0
 fi