doc/go1.17: add release note for windows/arm64 port

Updates #44513, #42604.

Change-Id: I8200e8087c219a0042ab2a6770a7275c3b17942a
Reviewed-on: https://go-review.googlesource.com/c/go/+/321309
Trust: Cherry Mui <cherryyz@google.com>
Reviewed-by: Dmitri Shuralyov <dmitshur@golang.org>

doc/go1.17.html

@@ -43,6 +43,13 @@ <h3 id="darwin">Darwin</h3>
   for previous versions has been discontinued.
 </p>
 
+<h3 id="windows">Windows</h3>
+
+<p><!-- golang.org/issue/36439 -->
+  Go 1.17 adds support of 64-bit ARM architecture on Windows (the
+  <code>windows/arm64</code> port). This port supports cgo.
+</p>
+
 <p>
   TODO: complete the Ports section
 </p>