fix: don't download images sourced from other domains

All media that's sourced from the domain other that the given domain (as
well as its www counterpart) will not be downloaded and will instead be
referenced externally as-is.

src/wp2hugo/internal/hugogenerator/hugo_gen_setup.go

@@ -434,7 +434,8 @@ func (g Generator) downloadPageMedia(outputMediaDirPath string, p *hugopage.Page
 			log.Warn().
 				Str("link", link).
 				Str("source", pageURL.String()).
-				Msg("non-relative link")
+				Msg("non-relative link (skipped for download)")
+			continue
 		}
 		outputFilePath := fmt.Sprintf("%s/static/%s", outputMediaDirPath,
 			strings.TrimSuffix(strings.Split(link, "?")[0], "/"))