Add website to DESCRIPTION

[olivroy]

to improve discoverability https://blog.r-hub.io/2019/12/10/urls/

Types of changes

• [ ] Bug fix (non-breaking change which fixes an issue)
• [x] New feature (non-breaking change which adds functionality)
• [ ] Breaking change (fix or feature that would cause existing functionality to change)
• [x] I have read the CONTRIBUTING document.
• [x] My code follows the code style of this project.
• [ ] My change requires a change to the documentation.
• [ ] I have updated the documentation accordingly.
• [ ] I have added tests to cover my changes.
• [x] All new and existing tests passed.

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Comparison is base (8405704) 93.68% compared to head (60589b5) 93.68%.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## devel #180 +/- ## ======================================= Coverage 93.68% 93.68% ======================================= Files 46 46 Lines 2961 2961 ======================================= Hits 2774 2774 Misses 187 187 ```

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[mstackhouse]

Thanks for the suggestion!