Add maskStyleClass property in DialogService

[sameerthekhans]

I'm submitting a ... (check one with "x")

[x] bug report => Search github for a similar issue or PR before submitting
[] feature request => Please check if request is not on the roadmap already https://github.com/primefaces/primeng/wiki/Roadmap
[ ] support request => Please do not submit support request here, instead see http://forum.primefaces.org/viewforum.php?f=35

Current behavior

this.dialogService.open(ConfirmationDialogComponent, {
  styleClass: 'custom-style-class',
  maskStyleClass: 'custom-mask-class' //cannot add
});

Expected behavior

this.dialogService.open(ConfirmationDialogComponent, {
  styleClass: 'custom-style-class',
  maskStyleClass: 'custom-mask-class' //should be able to add
});

Please tell us about your environment:

• Angular version: 5.X
  11.2.10

• PrimeNG version: 5.X
  11.4.5

• Browser: [all | Chrome XX | Firefox XX | IE XX | Safari XX | Mobile Chrome XX | Android X.X Web Browser | iOS XX Safari | iOS XX UIWebView | iOS XX WKWebView ]

• Language: [all | TypeScript X.X | ES6/7 | ES5]

• Node (for AoT issues): node --version = 14.17.5