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

[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%

---

Files with Coverage Reduction	New Missed Lines	%
pkg/controllers/provisioning/scheduling/nodeclaim.go	2	89.13%
pkg/controllers/disruption/consolidation.go	4	88.55%
<!--	Total:	6		-->

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

---

💛 - Coveralls

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: elmiko, jonathan-innis

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Needs approval from an approver in each of these files: - ~~[OWNERS](https://github.com/kubernetes-sigs/karpenter/blob/main/OWNERS)~~ [jonathan-innis] Approvers can indicate their approval by writing `/approve` in a comment Approvers can cancel approval by writing `/approve cancel` in a comment

[jonathan-innis]

Nice @elmiko!