Provide method to translate "Close" text

[weboverhauls]

The close button is modified for accessibility which works great. Part of this fix is using the word "Close" instead of "×". To enhance for internationalization, suggest adding the option to use a variable or a data attribute to get the text "Close" (or its translated text).

$('.close').removeAttr('aria-hidden').wrapInner('<span aria-hidden="true"></span>').append('<span class="sr-only">Close</span>')

[weboverhauls]

Clarification: This is for the Alert. (There no i18n issue with the "close" text for other items such as Modal because the text is in the HTML.)

[cvrebert]

I don't think this is an issue anymore thanks to twbs/bootstrap#13493 ?

[weboverhauls]

Hey, thanks for the PR. I did notice this improvement after I started digging into things, so closing.