fix(build): isBs3() function not work properly with chrome + unzoom + windows

[FightTheWar]

Bug description or feature request:

isBs3() function not work properly with chrome in some situation
You can try the example whith Chrome browser, unzoom to 50% and reload the page
First the function return true, the after relaod it will be false

The problem come from utils/theme-provider.js
In _guessBsVersion() you test rect.top === 0
But with unzoom this test can be true with Bootstrap 3 + chrome

Plunker/StackBlitz that reproduces the issue:

https://plnkr.co/edit/ZFXpDBBcOegQyKjByMEi?p=preview

Versions of ngx-bootstrap, Angular, and Bootstrap:

ngx-bootstrap: 2.0.0-rc.0
Angular: 5.1.2
Bootstrap: 3.3.7
Chrome version 63.0.3239.132

[IlyaSurmay]

Works fine on my machine

modified plunker with bigger font - https://plnkr.co/edit/5xc2i4DpnEAbAnvqYwnp?p=preview

[FightTheWar]

Did you reload the page ? And try without font size modification

I'm using Windows 7 and we have the same problem on every laptop in the company

This is not a big issue because we can fix the right version at startup

[valorkin]

@IlyaSurmay did you cleaned local storage before testing? :)

[valorkin]

ok, I can not reproduce it too

[valorkin]

@IlyaSurmay need to try on windows

[FightTheWar]

Hello, I confirm, it occurs only under windows