Invert control of loading

[chimon2000]

Is your feature request related to a problem? Please describe.

Currently, the future is executed soon as the widget is rendered. Should allow for more fine grained control of loading.

Describe the solution you'd like

Add a loadOnMount property

• Triggers whether or not the future is executed on default
• Default to true

Add a load function to builder props.

• Triggers load / reload future when executed

Describe alternatives you've considered

N/A

Additional context

https://github.com/jxom/react-loads#loadonmount