internal: improve docstrings of internal and derrors

Change-Id: I5e78b5ca9391229e1a45fec941c2febb78b72501
Reviewed-on: https://go-review.googlesource.com/c/pkgsite-metrics/+/480016
Reviewed-by: Jonathan Amsterdam <jba@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Run-TryBot: Zvonimir Pavlinovic <zpavlinovic@google.com>
diff --git a/internal/derrors/derrors.go b/internal/derrors/derrors.go
index d18768e..f5bdaeb 100644
--- a/internal/derrors/derrors.go
+++ b/internal/derrors/derrors.go
@@ -3,7 +3,7 @@
 // license that can be found in the LICENSE file.
 
 // Package derrors defines internal error values to categorize the different
-// types error semantics.
+// types of semantic errors.
 package derrors
 
 import (
diff --git a/internal/goenv.go b/internal/goenv.go
index 7a10b76..25844e3 100644
--- a/internal/goenv.go
+++ b/internal/goenv.go
@@ -2,6 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
+// Package internal contains mostly utility functions.
 package internal
 
 import (