Mui-datatables: onSearchOpen callback (similar to current onSearchClose only triggering when the search icon is clicked)

[apercas]

Expected Behavior

As we already have onSearchClose (see https://github.com/gregnb/mui-datatables/issues/145) I think we can also use a similar callback for when a user opens the search dialog and showSearch is true.

Current Behavior

The searchbox is opened offering a "value has changed" and "box has been closed" callback, but not for "box has been opened"

Thank you very much :)

[gregnb]

Sure, would you like to submit a PR for this?

[apercas]

Will do.