iNaturalist identifier leaderboard

This uses the iNaturalist identifications/identifiers API to construct a leaderboard of identifiers. It's intended use is to track stats in IDaThons, e.g., a leaderboard of identifications for a particular time period. It can be embedded as an iFrame on iNaturalist journal posts, for example, the following restricts the leaderboard to vascular plants in Oregon between 9/20/24 and 9/26/24:

<iframe src="https://herbarium.science.oregonstate.edu/iNat/id-leaderboard.php?own_observation=false&is_change=false&place_id=10&taxon_id=211194&d1=2024-09-20T00:00-08:00&d2=2024-09-26T23:59-08:00" height="300" width="450" frameborder="0"><iframe>

Any variables from the api reference can be added as link parameters to constrain the leaderboard, and this help text will disappear when embedded in an iframe within a journal post.