Add Linux arm64 platform support

Fixes #62

Author: ahmetb

.krew.yaml

@@ -33,6 +33,12 @@ spec:
         arch: amd64
     {{addURIAndSha "https://github.com/ahmetb/kubectl-tree/releases/download/{{ .TagName }}/kubectl-tree_{{ .TagName }}_linux_amd64.tar.gz" .TagName }}
     bin: kubectl-tree
+  - selector:
+      matchLabels:
+        os: linux
+        arch: arm64
+    {{addURIAndSha "https://github.com/ahmetb/kubectl-tree/releases/download/{{ .TagName }}/kubectl-tree_{{ .TagName }}_linux_arm64.tar.gz" .TagName }}
+    bin: kubectl-tree
   - selector:
       matchLabels:
         os: windows