Clarify use of non-standard "align" attribute for mat-dialog-actions

[cwatzl]

Documentation Feedback

Documentation suggests using the align attribute to align the content of mat-dialog-actions directives to the middle or right. However, align is an obsolete HTML attribute and not valid HTML5, and my IDE's static code analysis tools rightfully complain about using it. If using align really is the right way of doing this regardless of W3C standards, this should be clarified in the docs (and possibly be explicitly declared as a property of the MatDialogActions directive to make IDEs stop complaining).

Affected documentation page: https://material.angular.io/components/dialog/overview

[crisbeto]

The dialog isn't meant to use the align attribute, but align is a custom attribute. It didn't make sense to turn it into an input, because it's only used for styling.

[devversion]

I would agree that this is confusing. Given that align is not standard for HTMLDivElement, I think it would make sense to turn this into an input w/ documentation (that would also help w/ type-checking; IDE's and bindings).

https://developer.mozilla.org/en-US/docs/Web/API/HTMLDivElement

[PooSham]

I could take this as my first issue I think. A fun christmas activity 😁🎅

[PooSham]

Question: Would adding an input and removing the css code count as feat, fix or docs in the type when I commit? I think it's hard to classify things like this.

[PooSham]

As of now, my solution would be a breaking for those using [attr.align]="x". I'd assume this is a very special case, probably only used for demo apps. Should I solve it in some other way, such as adding an input that is called justify and keep the old scss code for backwards compability?