Custom row/column information mouseover

[cornhundred]

Users should be able to pass a row/column dictionary with additional information (e.g. longer names or other information) as an argument. This will display when mousing over rows/columns instead of making a GET request to the Harmonizome.

For instance

• Row mouseover should give the full definition of these NBA stats:
  https://www.kaggle.com/cornhundred/heatmap-view-of-modern-era-player-stats?scriptVersionId=15969060
• Custom surface marker information (e.g. in house surface marker information) can be given as a mouseover and this small dictionary can be loaded into the notebook without having to make GET requests to some server.