Add an 'ibm' extra package

[tomwhite]

Part of #1324

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[JosepSampe]

Not sure if you want to tackle this here, but the kubernetes package is also required by IBM Code Engine, so it should be placed inside IBM extra. In consequence, you should also create lithops[kubernetes] and lithops[knative] containing the kubernetes package

[tomwhite]

Thanks for the guidance @JosepSampe. How does this look?

[JosepSampe]

Great! From my side I'm fine with the change, but as I stated in the issue, I wanted to get @gilv's approval, as IBM packages have been always in the default installation

[JosepSampe]

@gilv Any comment/objection on this? If no, I will proceed to merge it

[JosepSampe]

@tomwhite can you update the IBM CE and IBM VPC docs and include the installation step?