fix(button): removed dotted outline in firefox

[bmdalex]

Button

This PR removes the dotted outline in Firefox for Button component. Repro:

• go to doc site in Firefox;
• navigate to the buttons using keyboard navigation;
• observe focus outline.

Before

After

[bmdalex]

@levithomason
@kuzhelov
pls take a look at my comments

[codecov]

Codecov Report

Merging #390 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #390   +/-   ##
=======================================
  Coverage   91.64%   91.64%           
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  Files          41       41           
  Lines        1341     1341           
  Branches      197      172   -25     
=======================================
  Hits         1229     1229           
  Misses        108      108           
  Partials        4        4

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[notandrew]

I don't think the changes should be made within normalize -- if we update to a new version of normalize, this change will be lost. Should it go into CustomCSS or siteVariables?

[kuzhelov]

great point, thanks @notandrew - that's definitely would be a better approach 👍

[bmdalex]

@kuzhelov
addressed @notandrew 's comments and moved the change in the semanticCssOverrides overrides file as per our discussion; ready to merge?

[levithomason]

This will only work in the doc site, is that the intent? If this should be the style for all usages of the Teams theme, including outside of the doc site by consumers, then this should be a staticStyle in the Teams theme. This way, everywhere the Teams theme is used, there is no outline in Firefox.

[kuzhelov]

for now yes, the intent was just to address doc site issue and propose a question of whether the same change should be applied for Teams theme.