Proposal template: explicitly mention RFC 3552 in security section (#4378)

* Template: explicitly mention RFC 3552 in security section

Signed-off-by: codedust <codedust@users.noreply.github.com>

* Apply suggestions from code review

---------

Signed-off-by: codedust <codedust@users.noreply.github.com>
Co-authored-by: Travis Ralston <travpc@gmail.com>

proposals/0000-proposal-template.md

@@ -87,7 +87,8 @@ idea.
 
 **All proposals must now have this section, even if it is to say there are no security issues.**
 
-*Think about how to attack your proposal, using lists from sources like
+*Think about how to attack your proposal. See [RFC 3552](https://datatracker.ietf.org/doc/html/rfc3552)
+for things to think about, but in particular pay attention to lists from sources like
 [OWASP Top Ten](https://owasp.org/www-project-top-ten/) for inspiration.*
 
 *Some proposals may have some security aspect to them that was addressed in the proposed solution. This