chore: pepr build custom image (#1401)

## Description

Builds a Pepr module and read manifests from known locations to assert
that the custom image was used.

CI test for `npx pepr build --custom-image'

End to End Test:  <!-- if applicable -->  
(See [Pepr Excellent
Examples](https://github.com/defenseunicorns/pepr-excellent-examples))

## Related Issue

Fixes #1370 
<!-- or -->
Relates to #

## Type of change

- [ ] Bug fix (non-breaking change which fixes an issue)
- [ ] New feature (non-breaking change which adds functionality)
- [x] Other (security config, docs update, etc)

## Checklist before merging
- [x] Unit,
[Journey](https://github.com/defenseunicorns/pepr/tree/main/journey),
[E2E Tests](https://github.com/defenseunicorns/pepr-excellent-examples),
[docs](https://github.com/defenseunicorns/pepr/tree/main/docs),
[adr](https://github.com/defenseunicorns/pepr/tree/main/adr) added or
updated as needed
- [x] [Contributor Guide
Steps](https://docs.pepr.dev/main/contribute/#submitting-a-pull-request)
followed

---------

Signed-off-by: Case Wylie <cmwylie19@defenseunicorns.com>

.github/workflows/cli-tests.yml

@@ -74,4 +74,40 @@ jobs:
           RESULT_FILE="stdin-module/package.json"
           grep "stdin-module" $RESULT_FILE
           grep "Set by flag" $RESULT_FILE
-          grep "reject" $RESULT_FILE
+          grep "reject" $RESULT_FILE
+
+      - name: pepr build --custom-image - generates Kubernetes manifest with a custom image
+        run: |
+          cd "${GITHUB_WORKSPACE}"
+          npx pepr@latest init \
+            --name=custom-image \
+            --description="custom image test" \
+            --errorBehavior=reject \
+            --skip-post-init \
+            --confirm
+          cd custom-image
+          npm i
+          npx ts-node ../pepr/src/cli.ts build --custom-image pepr:dev
+          UUID=$(cat package.json | jq -r .pepr.uuid)
+          count=$(cat dist/$UUID-chart/values.yaml | egrep "image: 'pepr:dev'" | wc -l)
+          if [ "$count" -eq 2 ]; then
+            echo "✅ Generated correct image for helm values."
+          else
+            echo "❌ Generated incorrect image for helm values."
+            exit 1
+          fi
+          count=$(cat dist/pepr-module-$UUID.yaml | egrep "pepr:dev" | wc -l)
+          if [ "$count" -eq 2 ]; then
+            echo "✅ Generated correct image for Pepr manifest."
+          else
+            echo "❌ Generated incorrect image for Pepr manifest."
+            exit 1
+          fi
+          count=$(cat dist/zarf.yaml | egrep "pepr:dev" | wc -l)
+          if [ "$count" -eq 1 ]; then
+            echo "✅ Generated correct image for Zarf manifest."
+          else
+            echo "❌ Generated incorrect image for Zarf manifest."
+            exit 1
+          fi
+