NzPageHeader: nzBack default implementation

[wbison]

What problem does this feature solve?

There is only one way to go 'back' - why force users to write code for that.

What does the proposed API look like?

Clicking the back icon in NzPageHeader component doesn't do anything. I have to write

back() {
    this.location.back();
}

and

<nz-page-header nzBackIcon (nzBack)='back()'>

to make it work. Could this behaviour be the default?

Note:
the docs on https://ng.ant.design/components/page-header/en specify [nzBack]
but this should be (nzBack) I think.