Add support to create_pod to support launching spot pods

[arnaudaz]

Is your feature request related to a problem? Please describe.
For quick jobs, spot is a great option. Unfortunately, the python library for runpod does not seem to support creating a spot pod, and forces on-demand.

Describe the solution you'd like
Add support for spot pod creation in the library, ideally as a parameter to the create_pod option or something similar.

Describe alternatives you've considered
Doing it in the UI, which is not helpful for automated jobs.

Additional context
N/A

[bigminions]

Yes, it's really important for our jobs

[ssep1ol]

Hello, it would be so much useful to me, to have that functionality