Add minimum k8s version in Helm (#2025)

Problem: The minimum version of k8s is not enforced in Helm. This would cause problems for people trying to install our chart in an unsupported version of k8s.

Solution: Add the minimum supported version in Chart.yaml

charts/nginx-gateway-fabric/Chart.yaml

@@ -4,6 +4,7 @@ description: NGINX Gateway Fabric
 type: application
 version: 1.2.0
 appVersion: "edge"
+kubeVersion: ">= 1.25.0-0"
 home: https://github.com/nginxinc/nginx-gateway-fabric
 icon: https://raw.githubusercontent.com/nginxinc/nginx-gateway-fabric/main/charts/nginx-gateway-fabric/chart-icon.png
 sources: