Remove the need for AWS credentials

[vmtzkr]

Hello,
I really appreciate this plugin, but currently experience an issue when no environment variables for the AWS credentials are set. After sls offline start the 5 seconds timeout occurs and I see following output.

Credentials Error --------------------------------------

Error: connect EHOSTUNREACH 169.254.169.254:80 - Local (192.168.101.1:49673)
at internalConnect (net.js:923:16)
at defaultTriggerAsyncIdScope (internal/async_hooks.js:364:12)
at net.js:1011:9
at processTicksAndRejections (internal/process/task_queues.js:79:11)
at runNextTicks (internal/process/task_queues.js:66:3)
at processTimers (internal/timers.js:494:9)

I don't have any credentials in the ~/.aws/ folder, since I'm using temporary tokens generated by the AWS SSO service. Would it be possible to add following configuration variables accessKeyId and secretAccessKey as in this referenced plugin? This way it would be possible to run this plugin without any AWS credentials set.