add cluster-api provider to readme

[elmiko]

Fixes #N/A

Description

update the readme to contain a reference to the cluster-api provider for karpenter.

How was this change tested?

N/A

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is NOT APPROVED

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[coveralls]

Pull Request Test Coverage Report for Build 11862280669

Details

• 0 of 0 changed or added relevant lines in 0 files are covered.
• 6 unchanged lines in 2 files lost coverage.
• Overall coverage decreased (-0.04%) to 80.993%

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Files with Coverage Reduction	New Missed Lines	%
pkg/controllers/provisioning/scheduling/nodeclaim.go	2	89.13%
pkg/controllers/disruption/consolidation.go	4	88.55%

Totals
Change from base Build 11861232184:	-0.04%
Covered Lines:	8595
Relevant Lines:	10612

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💛 - Coveralls