add arm64 build

.drone.yml

@@ -1,6 +1,6 @@
 kind: pipeline
 type: docker
-name: unstable
+name: amd64
 
 platform:
   os: linux
@@ -20,3 +20,26 @@ steps:
       from_secret: docker_token
     build_args:
       - TARGETPLATFORM=linux/amd64
+
+---
+kind: pipeline
+type: docker
+name: arm64
+
+platform:
+  os: linux
+  arch: arm64
+
+steps:
+- name: docker
+  image: plugins/docker
+  settings:
+    repo: bbilly1/tubearchivist-test
+    tags:
+      - unstable
+    username:
+      from_secret: docker_username
+    password:
+      from_secret: docker_token
+    build_args:
+      - TARGETPLATFORM=linux/arm64