Add security policy (#2245)

Signed-off-by: Pedro Kaj Kjellerup Nacht <pnacht@google.com>
Co-authored-by: Keith Winstein <keithw@cs.stanford.edu>

Author: pnacht

SECURITY.md

@@ -0,0 +1,14 @@
+# Security Policy
+
+WABT is maintained by volunteers on a reasonable-effort basis. If you
+have discovered a security vulnerability, please open a GitHub issue
+to report it. In the future, we may move to a system of private
+reporting of security issues. Please submit your report by filling out
+[this form](https://github.com/WebAssembly/wabt/issues/new).
+
+Please provide the following information in your report:
+
+- A description of the vulnerability and its impact
+- How to reproduce the issue
+- Which WABT tools or library functions are affected
+- Which WebAssembly features (`--enable` flags) must be enabled