API reference pages for plugins should provide link to associated plugin repo

[jwasilgeo]

Example of expected situation

The API reference page for the L.esri.Geocoding.Geosearch includes a link to the repo of the plugin.

Recommended changes

A couple other API references pages for plugins do not provide this, but I think they should for convenience.

• https://esri.github.io/esri-leaflet/api-reference/layers/heatmap-feature-layer.html
• https://esri.github.io/esri-leaflet/api-reference/layers/cluster-feature-layer.html