added CONTRIBUTING and SECURITY md files in .github

.github/SECURITY.md

@@ -0,0 +1,9 @@
+send security bug reports to security@beefproject.com
+
+**A security report should include:**
+
+1. Description of the problem (what it is, what's the impact)
+
+2. Technical steps to replicate it (commands / screenshots)
+
+3. Actionable fix/recommendations to mitigate the issue