Update install-kubectl.sh

Checks and applies correct CPU architecture.

docs/install-kubectl.sh

@@ -6,9 +6,18 @@ umask 077
 api_url="https://storage.googleapis.com/kubernetes-release/release"
 version="$(curl -s ${api_url}/stable.txt)"
 platform="$(uname -s | tr "[:upper:]" "[:lower:]")"
+arch="$(uname -m)"
+if [ "$arch" = "x86_64" ]; then
+  arch="amd64"
+elif [ "$arch" = "arm64" ] || [ "$arch" = "aarch64" ]; then
+  arch="arm64"
+else
+  echo "Unsupported architecture: $arch"
+  exit 1
+fi
 
 mkdir -p /tmp/kubectl && cd /tmp/kubectl
-curl -LO "${api_url}/${version}/bin/${platform}/amd64/kubectl"
+curl -LO "${api_url}/${version}/bin/${platform}/${arch}/kubectl"
 chmod +x kubectl
 sudo mkdir -p /usr/local/bin
 sudo mv kubectl /usr/local/bin/