Add CODEOWNERS for emerge-tools team (#2794)

Co-authored-by: Daniel Szoke <7881302+szokeasaurusrex@users.noreply.github.com>

Author: trevor-e

.github/CODEOWNERS

@@ -1 +1,5 @@
 * @szokeasaurusrex @getsentry/owners-sentry-cli
+
+/src/commands/build @getsentry/emerge-tools @getsentry/owners-sentry-cli
+/src/utils/build @getsentry/emerge-tools @getsentry/owners-sentry-cli
+/tests/integration/build @getsentry/emerge-tools @getsentry/owners-sentry-cli