fix: improve error handling and create the json encoder once #331 (#332)

* fix: improve error handling for resource closing and JSON encoding in MakeChallenge

* chore: update CHANGELOG with recent changes and improvements

* refactor: simplify RenderIndex function and improve error handling

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Signed-off-by: Jason Cameron <git@jasoncameron.dev>

cmd/containerbuild/main.go

@@ -131,7 +131,7 @@ func parseImageList(imageList string) ([]image, error) {
 	}
 
 	if len(result) == 0 {
-		return nil, fmt.Errorf("no images provided, bad flags??")
+		return nil, fmt.Errorf("no images provided, bad flags")
 	}
 
 	return result, nil