Add plugin for support asynchronous storage

v3/plugins/eclipse/che-async-pv-plugin/latest.txt

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+nightly

v3/plugins/eclipse/che-async-pv-plugin/nightly/meta.yaml

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+apiVersion: v2
+publisher: eclipse
+name: che-async-pv-plugin
+version: nightly
+type: Che Plugin
+displayName: Che Async Storage Service
+title: Che Async Storage Service Plugin
+description: Che Plug-in with service to provide abilty for backup/restore project source from async storage
+icon: https://www.eclipse.org/che/images/logo-eclipseche.svg
+repository: https://github.com/che-incubator/workspace-data-sync
+firstPublicationDate: "2020-07-10"
+category: Other
+spec:
+  endpoints:
+   -  name: "che-rsync-events"
+      public: true
+      targetPort: 4445
+      attributes:
+        protocol: ws
+        type: rsync
+        discoverable: false
+        secure: false
+        cookiesAuthEnabled: true
+  containers:
+   - name: che-rsync
+     image: "quay.io/eclipse/che-sidecar-workspace-data-sync:latest"
+     memoryLimit: "512M"
+     lifecycle:
+      preStop:
+        exec:
+          command: ["/bin/sh", "-c", "/scripts/backup.sh"] 
+     mountSources: true
+     ports:
+       - exposedPort: 4445
+     env:
+         - name: RSYNC_PORT
+           value: "2222"