[Button] render button in focused state

[sijad]

Feature request summary

allow render a Button in its focused state.

Rationale

1. buttons that opens a popover need to be in their focused state when popover opened.
2. sometimes button need to be in focused state a in WYSIWYG editor toolbar.

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[dleroux]

Hi @sijad, Thanks for the feature request but it looks like you'll be able to do this when this PR merges: #2148. I'll close this for now, reopen it that isn't the case.