SUPPORT.MD: Mark LiveUpdate of C/OCaml xenstored daemon as Tech Preview

Support to liveupdate C/OCaml xenstored daemon was added during the
4.15 development cycle. Add two new sections in SUPPORT.MD to explain
what is the support state.

For now, it is a tech preview.

Signed-off-by: Julien Grall <jgrall@amazon.com>
Reviewed-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Andrew Cooper <andrew.cooper3@citrix.com>
Release-Acked-by: Ian Jackson <iwj@xenproject.org>

SUPPORT.md

@@ -177,6 +177,14 @@ Support for running qemu-xen device model in a linux stubdomain.
 
     Status: Tech Preview
 
+## Liveupdate of C xenstored daemon
+
+    Status: Tech Preview
+
+## Liveupdate of OCaml xenstored daemon
+
+    Status: Tech Preview
+
 ## Toolstack/3rd party
 
 ### libvirt driver for xl