docs: update MAINTAINERS to a markdown

Signed-off-by: Niladri Halder <[email protected]>

Author: niladrih

MAINTAINERS

@@ -0,0 +1,8 @@
+# Maintainers
+
+## Umbrella Project
+
+OpenEBS is an `Umbrella Project` whose governance and policies are defined in the [community](https://github.com/openebs/community/) repository.
+These policies are applicable to every sub-project, repository and file existing within the [OpenEBS GitHub organization](https://github.com/openebs/).
+
+Please refer to the [OpenEBS Maintainers](https://github.com/openebs/community/blob/HEAD/MAINTAINERS.md).