_content/doc/install: add windows/arm and windows/arm64

This change adds windows/arm and windows/arm64 to the list of valid
$GOOS and $GOARCH combinations.

Fixes golang/go#47789.

Change-Id: Iac102758f816a856f504473c623ad880caf3b72b
Reviewed-on: https://go-review.googlesource.com/c/website/+/343216
Trust: Michael Knyszek <mknyszek@google.com>
Run-TryBot: Michael Knyszek <mknyszek@google.com>
Reviewed-by: Dmitri Shuralyov <dmitshur@golang.org>
diff --git a/_content/doc/install/source.html b/_content/doc/install/source.html
index e7b3dfc..4fff34f 100644
--- a/_content/doc/install/source.html
+++ b/_content/doc/install/source.html
@@ -671,6 +671,12 @@
 <tr>
 <td></td><td><code>windows</code></td> <td><code>amd64</code></td>
 </tr>
+<tr>
+<td></td><td><code>windows</code></td> <td><code>arm</code></td>
+</tr>
+<tr>
+<td></td><td><code>windows</code></td> <td><code>arm64</code></td>
+</tr>
 </table>
 
 <li><code>$GOHOSTOS</code> and <code>$GOHOSTARCH</code>