Feature Request: disable Missing API key warning

[HarimbolaSantatra]

Description
It would be nice to have an option to disable the Missing API key warning.

[!] Missing API key for Github.
Read api-keys.yaml from /home/santatra/.theHarvester/api-keys.yaml

[!] Missing API key for Hunter.
Read api-keys.yaml from /home/santatra/.theHarvester/api-keys.yaml

For example, something like a -s/--silent or a -q/--quiet flag.

Expected behaviour
Running theHarvester without any API key and with the -s/--silent flag would display the result without the Missing API keys warning.