feat(modal): add method to change modal window class

[ghost]

Was added:

• demo Change class
• functionality for changing modal's window class after the modal window was opened

Related to #2824

[codecov]

Codecov Report

Merging #4811 into development will increase coverage by 0.19%.
The diff coverage is 0%.

@@              Coverage Diff               @@
##           development   #4811      +/-   ##
==============================================
+ Coverage        74.51%   74.7%   +0.19%     
==============================================
  Files              273     276       +3     
  Lines             8365    8381      +16     
  Branches          1594    1594              
==============================================
+ Hits              6233    6261      +28     
+ Misses            1696    1681      -15     
- Partials           436     439       +3

Impacted Files	Coverage Δ
src/modal/bs-modal.service.ts	22.42% <0%> (-0.43%)	⬇️
src/modal/bs-modal-ref.service.ts	60% <0%> (-15%)	⬇️
src/chronos/i18n/pl.ts	69.23% <0%> (-2.57%)	⬇️
src/datepicker/reducer/bs-datepicker.effects.ts	72.47% <0%> (-1.84%)	⬇️
src/chronos/i18n/cs.ts	84.74% <0%> (ø)	⬆️
src/chronos/i18n/sk.ts	80.85% <0%> (ø)	⬆️
src/modal/index.ts	100% <0%> (ø)
src/modal/modal-backdrop.options.ts	50% <0%> (ø)
src/modal/public_api.ts	100% <0%> (ø)
src/typeahead/typeahead.directive.ts	74.86% <0%> (+1.04%)	⬆️
... and 4 more

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[Domainv]

needs add tests

[ludmilanesvitiy]

This is a view from FF 63.0.3
Need to fix button view for FF (should be centered or aligned to width as in Chrome)

[ghost]

can't reproduce

[ludmilanesvitiy]

Retested with different FF versions and diff OS, looks good.