Add default .ocm/branch-info.yaml file (gardener#330)

* Add default `.ocm/branch-info.yaml` file

* Update release cadence and release branch template name

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Co-authored-by: aaronfern <aaron.francis.fernandes@sap.com>

Author: 8R0WNI3

.ocm/branch-info.yaml

@@ -0,0 +1,5 @@
+release-branch-template: rel-v$major.$minor # e.g. rel-v1.0
+branch-policy:
+  significant-part: minor # major, minor, patch
+  supported-versions-count: 2
+  release-cadence: null # d (days), w (weeks), y | yr (years)