Updates for initial release of reports

The following models will need updates to their User Guide pages to accompany the launch of their reports in the InVEST 3.18.0 release: - Carbon - Coastal Vulnerability - NDR - SDR Specifically, we need to add the HTML report to the list of outputs in the "Interpreting Results" section. We may also want to add links to sample reports, or even embed images from sample reports, to give users a more immediate sense of what reports entail.