Improve ci/kind/kind-setup.sh usage (antrea-io#2937)

* Default "--antrea-cni" to false: most of the time, it is actually how
  we use it, and it is how users need to use the script.
* Check-in build/yamls/antrea-kind.yml to avoid user confusion.
* Improve Antrea with Kind documentation.

Fixes antrea-io#2934

Signed-off-by: Antonin Bas <abas@vmware.com>

Makefile

@@ -334,6 +334,7 @@ manifest:
 	$(CURDIR)/hack/generate-manifest.sh --mode dev --cloud EKS --encap-mode networkPolicyOnly > build/yamls/antrea-eks.yml
 	$(CURDIR)/hack/generate-manifest.sh --mode dev --cloud GKE --encap-mode noEncap > build/yamls/antrea-gke.yml
 	$(CURDIR)/hack/generate-manifest.sh --mode dev --cloud AKS --encap-mode networkPolicyOnly > build/yamls/antrea-aks.yml
+	$(CURDIR)/hack/generate-manifest.sh --mode dev --kind > build/yamls/antrea-kind.yml
 	$(CURDIR)/hack/generate-manifest-octant.sh --mode dev > build/yamls/antrea-octant.yml
 	$(CURDIR)/hack/generate-manifest-windows.sh --mode dev > build/yamls/antrea-windows.yml
 	$(CURDIR)/hack/generate-manifest-flow-aggregator.sh --mode dev > build/yamls/flow-aggregator.yml