Make select dropdown accessible through tab navigation
Make select dropdown accessible through tab navigation

- Map `TAB` key
- Store flagsContainer in `this.flagsContainer` to bind events to it
later
- Define `tabindex="0"` attribute so `div` is focusable
- Insert select element BEFORE `input` so tab navigation works as
expected (otherwise `input` is focused before the select)
- Handle "keydown" event on `this.flagsContainer` to `_showDropdown()`
on when the following keys are pressed: UP, DOWN, SPACE or ENTER. And
close dropdown when TAB is pressed

javimey/intl-tel-input,xetryj/intl-tel-input,ifeelgoods/intl-tel-input,Doncode/intl-tel-input,callpage/intl-tel-input,MartinReidy/intl-tel-input,callumacrae/intl-tel-input,fishman1986/intl-tel-input,geosub/intl-tel-input,MartinReidy/intl-tel-input,Doncode/intl-tel-input,PeterDaveHello/intl-tel-input,felipe-pereira/intl-tel-input,guilhermegm/intl-tel-input,callpage/intl-tel-input,jackocnr/intl-tel-input,mpmurph/intl-tel-input,javimey/intl-tel-input,classdojo/intl-tel-input,SureShinde/intl-tel-input,caseyjhol/intl-tel-input,fishman1986/intl-tel-input,nlwillia/intl-tel-input,felipe-pereira/intl-tel-input,unnutz/intl-tel-input,denim2x/international-phone-number,andriytkachiv/intl-tel-input,nlwillia/intl-tel-input,denim2x/international-phone-number,classdojo/intl-tel-input,Ahimta/intl-tel-input,Ahimta/intl-tel-input,guilhermegm/intl-tel-input,andriytkachiv/intl-tel-input,dragon-air/intl-tel-input,Bluefieldscom/intl-tel-input,thesocialstation/intl-tel-input,Ahimta/intl-tel-input,jackocnr/intl-tel-input,mpmurph/intl-tel-input,geosub/intl-tel-input,thesocialstation/intl-tel-input,callumacrae/intl-tel-input,dragon-air/intl-tel-input,PeterDaveHello/intl-tel-input,Bluefieldscom/intl-tel-input,SureShinde/intl-tel-input,caseyjhol/intl-tel-input,unnutz/intl-tel-input,ifeelgoods/intl-tel-input,xetryj/intl-tel-input