Loader needs a delay property

[johannao76]

Feature Request

Problem description

In some cases, loading happens immediately, in which case, we don't want the loading spinner to be rendered at all.

Proposed solution

Add a delay property to the Loader component to indicate how long to wait before showing it

[layershifter]

delay prop exists in:

• https://ant.design/components/spin/
• https://evergreen.segment.com/components/spinner/
• https://www.lightningdesignsystem.com/components/spinners/
• https://atlaskit.atlassian.com/packages/core/spinner

It doesn't changes the behavior of the component and can be safely implemented.