Add description of JSON file used to create cluster.
According to doco https://www.mongodb.com/docs/atlas/cli/upcoming/command/atlas-clusters-create/
"For full control of your deployment, or to create multi-cloud clusters, provide a JSON configuration file with the --file flag."
it would be nice to get detailed description what should be in this file, what can be changed and what is the expected format of parameters in this file.

Hi Sergey,
Apologies for the late response here and thank you for raising it in the first place.
In version 1.5.0 of the Atlas CLI we've updated the command's help to provide better guidelines and links to more details on the configuration file.
You'll see the following information
-f, --file string Path to an optional JSON configuration file that defines cluster settings. To learn more about configuration files for the Atlas CLI, see https://www.mongodb.com/docs/atlas/cli/stable/cluster-config-file/. To learn more about configuration files for MongoCLI, see https://www.mongodb.com/docs/mongocli/stable/reference/mms-cluster-settings-file/.
Please let me know if there's anything unclear.
Thanks,
Jakub