doc: add a release notes blurb on 1.16 linker improvements

Add a draft version of a blurb on improvements to the linker. This
will need to be finalized later in the release since there are still
some additional changes to be made to the linker in 1.16.

Updates #40703.

Change-Id: Id85c7e129071cc2faacb09c53a2968bd52b0a7b4
Reviewed-on: https://go-review.googlesource.com/c/go/+/248238
Reviewed-by: Cherry Zhang <cherryyz@google.com>
Reviewed-by: Austin Clements <austin@google.com>
diff --git a/doc/go1.16.html b/doc/go1.16.html
index f0e26a1..1fea359 100644
--- a/doc/go1.16.html
+++ b/doc/go1.16.html
@@ -62,7 +62,26 @@
 <h2 id="linker">Linker</h2>
 
 <p>
-  TODO
+  This release includes additional improvements to the Go linker,
+  reducing linker resource usage (both time and memory) and improving
+  code robustness/maintainability. These changes form the second half
+  of a two-release project to
+  <a href="https://golang.org/s/better-linker">modernize the Go
+  linker</a>.
+</p>
+
+<p>
+  The linker changes in 1.16 extend the 1.15 improvements to all
+  supported architecture/OS combinations (the 1.15 performance improvements
+  were primarily focused on <code>ELF</code>-based OSes and
+  <code>amd64</code> architectures).  For a representative set of
+  large Go programs, linking is 20-35% faster than 1.15 and requires
+  5-15% less memory on average for <code>linux/amd64</code>, with larger
+  improvements for other architectures and OSes.
+</p>
+
+<p>
+  TODO: update with final numbers later in the release.
 </p>
 
 <h2 id="library">Core library</h2>