doc: release notes for text/scanner and text/template

Change-Id: Ib5417cc48959b03befb1579da3281415a11ede9f
Reviewed-on: https://go-review.googlesource.com/c/go/+/181879Reviewed-by: Dmitri Shuralyov <dmitshur@golang.org>

doc/go1.13.html

@@ -383,7 +383,8 @@ TODO
 <dl id="text/scanner"><dt><a href="/pkg/text/scanner/">text/scanner</a></dt>
   <dd>
     <p><!-- CL 163079 -->
-      TODO: <a href="https://golang.org/cl/163079">https://golang.org/cl/163079</a>: don&#39;t liberally consume (invalid) floats or underbars
+      The new <a href="/pkg/text/scanner/#AllowNumberbars"><code>AllowNumberbars</code></a>
+      mode allows number literals to contain underbars as digit separators.
     </p>
 
 </dl><!-- text/scanner -->
@@ -391,7 +392,8 @@ TODO
 <dl id="text/template"><dt><a href="/pkg/text/template/">text/template</a></dt>
   <dd>
     <p><!-- CL 161762 -->
-      TODO: <a href="https://golang.org/cl/161762">https://golang.org/cl/161762</a>: add a slice function to the predefined global functions
+      The new <a href="/pkg/text/template/#hdr-Functions">slice function</a>
+      returns the result of slicing its first argument by the following arguments.
     </p>
 
 </dl><!-- text/template -->