Add SECURITY.md

Add a SECURITY.md pointing to the main reference file. SECURITY.md
contains important information on how to report a vulnerability
in the Projects and helps security researchers to find the appropriate
communication method.

Signed-off-by: Marta Rybczynska <marta.rybczynska@eclipse-foundation.org>

SECURITY.md

@@ -0,0 +1,3 @@
+# How To Report a Vulnerability
+
+See https://github.com/eclipse-platform/.github/blob/main/SECURITY.md