add dennis to codeowners (#33147)

## Summary & Motivation

Add @dehume to CODEOWNERS to review changes to examples and Dagster
basics tutorial.

## How I Tested These Changes

N/A

## Changelog

> Insert changelog entry or delete this section.

Signed-off-by: nikki everett <nikki@dagsterlabs.com>

Author: neverett

.github/CODEOWNERS

@@ -1,2 +1,6 @@
 # Automatically request docs team for docs PR review
-/docs/              @dagster-io/docs
+/docs/                                  @dagster-io/docs
+
+# Automatically request education team for examples and basics tutorial PR review
+/docs/docs/examples                     @dehume
+/docs/docs/dagster-basics-tutorial      @dehume