Adding FOSSA configuration

.fossa.yml

+# Generated by FOSSA CLI (https://github.com/fossas/fossa-cli)
+# Visit https://fossa.com to learn more
+
+version: 2
+cli:
+  server: https://app.fossa.com
+  fetcher: custom
+  project: os-notification
+analyze:
+  modules:
+  - name: os-notification
+    type: mvn
+    target: pom.xml
+    path: .
+  - name: notification-core
+    type: mvn
+    target: notification-core/pom.xml
+    path: .
+  - name: notification-gcp
+    type: mvn
+    target: provider/notification-gcp/pom.xml
+    path: .