internal/history: document Go 1.15.6 and Go 1.14.13

Updates golang/go#42973
Updates golang/go#42974

Change-Id: I3c6f12238e7b36a079d399f45c0974512badf6a4
Reviewed-on: https://go-review.googlesource.com/c/website/+/275116
Trust: Carlos Amedee <carlos@golang.org>
Run-TryBot: Carlos Amedee <carlos@golang.org>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Dmitri Shuralyov <dmitshur@golang.org>
diff --git a/internal/history/release.go b/internal/history/release.go
index 2d9db8a..f32f25e 100644
--- a/internal/history/release.go
+++ b/internal/history/release.go
@@ -31,15 +31,31 @@
 // It contains entries for releases of Go 1.9 and newer.
 // Older releases are listed in doc/devel/release.html.
 var Releases = map[GoVer]Release{
+	{1, 15, 6}: {
+		Date: Date{2020, 12, 3},
+
+		Components: []template.HTML{"the compiler", "linker", "runtime", "the <code>go</code> command"},
+		Packages:   []string{"io"},
+	},
+	{1, 14, 13}: {
+		Date: Date{2020, 12, 3},
+
+		Components: []template.HTML{"the compiler", "runtime", "the <code>go</code> command"},
+	},
+
 	{1, 15, 5}: {
 		Date:     Date{2020, 11, 12},
 		Security: true,
-		Packages: []string{"cmd/go", "math/big"},
+
+		Components: []template.HTML{"the <code>go</code> command"},
+		Packages:   []string{"math/big"},
 	},
 	{1, 14, 12}: {
 		Date:     Date{2020, 11, 12},
 		Security: true,
-		Packages: []string{"cmd/go", "math/big"},
+
+		Components: []template.HTML{"the <code>go</code> command"},
+		Packages:   []string{"math/big"},
 	},
 
 	{1, 15, 4}: {