An extra space space after:
--mount type=volume,src=todo-db,
gives the following error:
invalid argument "type=volume,src=todo-db" for "--mount" flag: target is required
See 'docker run --help'.
Make the cat command check for the file that the user created.
In the current version, the user makes a file called 'greeting.txt' but then checks for a file called 'greetings.txt'.