doc: revise help page with categories and more links

Fixes #12489

Change-Id: I25dd3f76e4cfe9a71b987c3b31445724568391e9
Reviewed-on: https://go-review.googlesource.com/18625Reviewed-by: Russ Cox <rsc@golang.org>

doc/help.html

 <!--{
-	"Title": "Getting Help",
+	"Title": "Help",
 	"Path": "/help/"
 }-->
 
-<img class="gopher" src="/doc/gopher/help.png"/>
-
-<p>
-Need help with Go? Try these resources.
-</p>
-
 <div id="manual-nav"></div>
 
-<h3 id="faq"><a href="/doc/faq">Frequently Asked Questions (FAQ)</a></h3>
-<p>Answers to common questions about Go.</p>
+<h2 id="help">Get help</h2>
 
-<h3 id="playground"><a href="/play">The Go Playground</a></h3>
-<p>A place to write, run, and share Go code.</p>
-
-<h3 id="wiki"><a href="/wiki">The Go Wiki</a></h3>
-<p>A wiki maintained by the Go community.</p>
+<img class="gopher" src="/doc/gopher/help.png"/>
 
-<h3 id="mailinglist"><a href="//groups.google.com/group/golang-nuts">Go Nuts Mailing List</a></h3>
+<h3 id="mailinglist"><a href="https://groups.google.com/group/golang-nuts">Go Nuts Mailing List</a></h3>
 <p>
-Search the <a href="//groups.google.com/group/golang-nuts">golang-nuts</a>
+Search the <a href="https://groups.google.com/group/golang-nuts">golang-nuts</a>
 archives and consult the <a href="/doc/go_faq.html">FAQ</a> and
 <a href="//golang.org/wiki">wiki</a> before posting.
 </p>
 
+<h3 id="forum"><a href="https://forum.golangbridge.org/">Go Forum</a></h3>
+<p>
+The <a href="https://forum.golangbridge.org/">Go Forum</a> is an alternate discussion
+forum for Go programmers.
+</p>
+
+<h3 id="slack"><a href="https://blog.gopheracademy.com/gophers-slack-community/">Gopher Slack</a></h3>
+<p>Get live support from the official Go slack channel.</p>
+
 <h3 id="irc"><a href="irc:irc.freenode.net/go-nuts">Go IRC Channel</a></h3>
 <p>Get live support at <b>#go-nuts</b> on <b>irc.freenode.net</b>, the official
 Go IRC channel.</p>
 
-<h3 id="pluscom"><a href="https://plus.google.com/communities/114112804251407510571">The Go+ community</a></h3>
-<p>The Google+ community for Go enthusiasts.</p>
+<h3 id="faq"><a href="/doc/faq">Frequently Asked Questions (FAQ)</a></h3>
+<p>Answers to common questions about Go.</p>
+
+<h2 id="inform">Stay informed</h2>
+
+<h3 id="announce"><a href="https://groups.google.com/group/golang-announce">Go Announcements Mailing List</a></h3>
+<p>
+Subscribe to
+<a href="https://groups.google.com/group/golang-announce">golang-announce</a>
+for important announcements, such as the availability of new Go releases.
+</p>
 
-<h3 id="plus"><a href="https://plus.google.com/101406623878176903605/posts">The Go Programming Language at Google+</a></h3>
-<p>The Go project's Google+ page.</p>
+<h3 id="blog"><a href="//blog.golang.org">Go Blog</a></h3>
+<p>The Go project's official blog.</p>
 
-<h3 id="twitter"><a href="//twitter.com/golang">@golang at Twitter</a></h3>
+<h3 id="twitter"><a href="https://twitter.com/golang">@golang at Twitter</a></h3>
 <p>The Go project's official Twitter account.</p>
-<p>Tweeting about your problem with the <code>#golang</code> hashtag usually
-generates some helpful responses.</p>
+
+<h3 id="pluscom"><a href="https://plus.google.com/communities/114112804251407510571">Go+ community</a></h3>
+<p>A Google+ community for Go enthusiasts.</p>
+
+<h3 id="reddit"><a href="https://reddit.com/r/golang">golang sub-Reddit</a></h3>
+<p>
+The <a href="https://reddit.com/r/golang">golang sub-Reddit</a> is a place
+for Go news and discussion.
+</p>
+
+<h2 id="community">Community resources</h2>
 
 <h3 id="go_user_groups"><a href="/wiki/GoUserGroups">Go User Groups</a></h3>
 <p>
@@ -48,6 +64,12 @@ Each month in places around the world, groups of Go programmers ("gophers")
 meet to talk about Go. Find a chapter near you.
 </p>
 
+<h3 id="playground"><a href="/play">Go Playground</a></h3>
+<p>A place to write, run, and share Go code.</p>
+
+<h3 id="wiki"><a href="/wiki">Go Wiki</a></h3>
+<p>A wiki maintained by the Go community.</p>
+
 <h3 id="conduct"><a href="/conduct">Code of Conduct</a></h3>
 <p>
 Guidelines for participating in Go community spaces