feat request: add the nzTrigger property for the nz-submenu

[ccppprogrammer]

What problem does this feature solve?

In some cases, for example, dropdown menus on header, we need to open submenu only when user clicks on it, and not when hovering, similar to nz-dropdown when nzTrigger property is set to click.

For example such a feature is on youtube or twitch (see pictures below):

What does the proposed API look like?

Property	Description	Type	Default
[nzTrigger]	the trigger mode which executes the drop-down action	'click' 'hover'	'hover'

when nzTrigger=hover - current behavior

when nzTrigger=click - open submenu only when user click on it

[TheAifam5]

I would like to see also same option for nz-menu.

[timothyBrake]

I would also want to see this option but for horizontal mode. Seems a missing feature for a basic menu like any menu system you see on your computer now. Any chance of implementing this as last post was 2020. Thanks in advance.

[chenweihan]

I would like to see also same option for nz-menu.