_content: add id links to security.html headings

Right now temporary ids like tmp_1 are being generated.
Put in something that will be more stable.

Change-Id: Ice223159dab1bdba4fa7126502a727c358bf3c52
Reviewed-on: https://go-review.googlesource.com/c/website/+/362117
Trust: Russ Cox <rsc@golang.org>
Run-TryBot: Russ Cox <rsc@golang.org>
TryBot-Result: Go Bot <gobot@golang.org>
Website-Publish: Russ Cox <rsc@golang.org>
Reviewed-by: Heschi Kreinick <heschi@google.com>

_content/security.html

@@ -2,14 +2,14 @@
 	"Title": "Go Security Policy"
 }-->
 
-<h2>Overview</h2>
+<h2 id="overview">Overview</h2>
 
 <p>
   This document explains the Go Security team's process for handling issues
   reported and what to expect in return.
 </p>
 
-<h2>Reporting a Security Bug</h2>
+<h2 id="reporting">Reporting a Security Bug</h2>
 
 <p>
   All security bugs in the Go distribution should be reported by email to
@@ -31,7 +31,7 @@
   <a href="mailto:security@golang.org">security@golang.org</a>.
 </p>
 
-<h2>Tracks</h2>
+<h2 id="tracks">Tracks</h2>
 
 <p>
   Depending on the nature of your issue, it will be categorized by the Go
@@ -39,7 +39,7 @@
   security issues will be issued CVE numbers.
 </p>
 
-<h3>PUBLIC</h3>
+<h3 id="public">PUBLIC</h3>
 <p>
   Issues in the PUBLIC track affect niche configurations, have very limited
   impact, or are already widely known.
@@ -85,7 +85,7 @@
   </li>
 </ul>
 
-<h3>PRIVATE</h3>
+<h3 id="private">PRIVATE</h3>
 
 <p>
   Issues in the PRIVATE track are violations of committed security properties.
@@ -135,7 +135,7 @@
   </li>
 </ul>
 
-<h3>URGENT</h3>
+<h3 id="urgent">URGENT</h3>
 
 <p>
   URGENT track issues are a threat to the Go ecosystem’s integrity, or are being
@@ -150,7 +150,7 @@
   with no pre-announcement.
 </p>
 
-<h2>Flagging Existing Issues as Security-related</h2>
+<h2 id="flagging">Flagging Existing Issues as Security-related</h2>
 
 <p>
   If you believe that an <a href="https://golang.org/issue">existing issue</a>
@@ -160,7 +160,7 @@
   according to this security policy.
 </p>
 
-<h2>Disclosure Process</h2>
+<h2 id="disclosure">Disclosure Process</h2>
 
 <p>The Go project uses the following disclosure process:</p>
 
@@ -207,7 +207,7 @@
   </a>.
 </p>
 
-<h2>Receiving Security Updates</h2>
+<h2 id="updates">Receiving Security Updates</h2>
 
 <p>
   The best way to receive security announcements is to subscribe to the
@@ -218,7 +218,7 @@
   with <code>[security]</code>.
 </p>
 
-<h2>Comments on This Policy</h2>
+<h2 id="comments">Comments on This Policy</h2>
 
 <p>
   If you have any suggestions to improve this policy, please