✨ announce where results are written (#4132)

Before this change, when running with '-o foo' the output would end
with:

```
RESULTS
-------
```

This was rather confusing. There's of course many ways to make this more
clear, this commit adds a log line announcing where the output is
written to:

```
RESULTS
-------
Writing to foo
```

Signed-off-by: Arnout Engelen <arnout@bzzt.net>

pkg/scorecard_result.go

@@ -134,6 +134,7 @@ func FormatResults(
 		if err != nil {
 			return fmt.Errorf("unable to create output file: %w", err)
 		}
+		fmt.Fprintln(os.Stderr, "Writing results to", opts.ResultsFile)
 		defer output.Close()
 	}