buildkite: add mantis-automation to pipeline (#1058)

Author: nrdxp

.buildkite/pipeline.yml

@@ -7,3 +7,7 @@ steps:
     agents:
       queue: project42
     timeout_in_minutes: 60
+  - label: "Mantis Automation"
+    command:
+    - "curl https://raw.githubusercontent.com/input-output-hk/mantis-automation/main/.buildkite/pipeline_erc20_pr.yml -o automation.yml"
+    - "buildkite-agent pipeline upload automation.yml"