Add yamlfmt #270

Job	Run time
test (clusterctl, ubuntu:latest)	24s
test-global	26s
test (clusterctl, fedora:latest)	25s
test (clusterctl, mcr.microsoft.com/devcontainers/base:ubuntu)	23s
test (kubeadm, ubuntu:latest)	18s
test (kubeadm, fedora:latest)	10s
test (kubeadm, mcr.microsoft.com/devcontainers/base:ubuntu)	20s
test (tilt, ubuntu:latest)	17s
test (tilt, fedora:latest)	12s
test (tilt, mcr.microsoft.com/devcontainers/base:ubuntu)	19s
test (kwok, ubuntu:latest)	20s
test (kwok, fedora:latest)	32s
test (kwok, mcr.microsoft.com/devcontainers/base:ubuntu)	20s
test (yamlfmt, ubuntu:latest)	13s
test (yamlfmt, fedora:latest)	15s
test (yamlfmt, mcr.microsoft.com/devcontainers/base:ubuntu)	23s
	5m 17s

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