internal/history: document Go 1.16.7 and Go 1.15.15

Change-Id: I7650239269944f3f48876cb57174ed9ffc63c1d1
Reviewed-on: https://go-review.googlesource.com/c/website/+/340169
Trust: Alexander Rakoczy <alex@golang.org>
Run-TryBot: Alexander Rakoczy <alex@golang.org>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Carlos Amedee <carlos@golang.org>
Reviewed-by: David Chase <drchase@google.com>
Website-Publish: DO NOT USE <dmitshur@google.com>
diff --git a/internal/history/release.go b/internal/history/release.go
index e14c615..9de918d 100644
--- a/internal/history/release.go
+++ b/internal/history/release.go
@@ -15,6 +15,22 @@
 // The table is sorted by date, breaking ties with newer versions first.
 var Releases = []*Release{
 	{
+		Date: Date{2021, 8, 5}, Version: Version{1, 16, 7},
+		CustomSummary: `includes a security fix to the <code>net/http/httputil</code> package,
+as well as bug fixes to the compiler, the linker, the runtime, the <code>go</code> command,
+and the <code>net/http</code> package. See the
+<a href="https://github.com/golang/go/issues?q=milestone%3AGo1.16.7+label%3ACherryPickApproved">Go
+1.16.7 milestone</a> on our issue tracker for details.`,
+	},
+	{
+		Date: Date{2021, 8, 5}, Version: Version{1, 15, 15},
+		CustomSummary: `includes a security fix to the <code>net/http/httputil</code> package,
+as well as bug fixes to the compiler, the runtime, the <code>go</code> command, and the
+<code>net/http</code> package. See the
+<a href="https://github.com/golang/go/issues?q=milestone%3AGo1.15.15+label%3ACherryPickApproved">Go
+1.15.15 milestone</a> on our issue tracker for details.`,
+	},
+	{
 		Date: Date{2021, 7, 12}, Version: Version{1, 16, 6},
 		CustomSummary: `includes a security fix to the <code>crypto/tls</code> package,
 as well as bug fixes to the compiler, and the <code>net</code> and <code>net/http</code> packages. See the