_content/doc/install: mention GOOS=wasip1

Updates golang/go#58141.

Change-Id: I7cfa8045ad9d27f1cc97bffb4ee2ac1a8c79e7c1
Reviewed-on: https://go-review.googlesource.com/c/website/+/495535
Run-TryBot: Cherry Mui <cherryyz@google.com>
Reviewed-by: Achille Roussel <achille.roussel@gmail.com>
Auto-Submit: Dmitri Shuralyov <dmitshur@golang.org>
Reviewed-by: Tianon Gravi (Andrew) <admwiggin@gmail.com>
Reviewed-by: Eli Bendersky <eliben@google.com>
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_content/doc/install/source.html

@@ -523,7 +523,8 @@ Choices for <code>$GOOS</code> are
 <code>android</code>, <code>darwin</code>, <code>dragonfly</code>,
 <code>freebsd</code>, <code>illumos</code>, <code>ios</code>, <code>js</code>,
 <code>linux</code>, <code>netbsd</code>, <code>openbsd</code>,
-<code>plan9</code>, <code>solaris</code> and <code>windows</code>.
+<code>plan9</code>, <code>solaris</code>, <code>wasip1</code>,
+and <code>windows</code>.
 </p>
 
 <p>
@@ -660,6 +661,9 @@ The valid combinations of <code>$GOOS</code> and <code>$GOARCH</code> are:
 <td></td><td><code>solaris</code></td> <td><code>amd64</code></td>
 </tr>
 <tr>
+<td></td><td><code>wasip1</code></td> <td><code>wasm</code></td>
+</tr>
+<tr>
 <td></td><td><code>windows</code></td> <td><code>386</code></td>
 </tr>
 <tr>