[Feature]: Observe onBlur events for text_extra

[federiva]

Guidelines

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Description

There are some situations in which listening to the onInput event might be too verbose for an app. It would be great to have an onBlur observable event in a shiny app

Problem

We need an onBlur event to be observed in a Shiny app

Proposed Solution

Add onBlur event when creating the React element

Alternatives Considered

Add manually the event after rendering the component in the browser