feat(ui5-menu-item): add endContent slot

[NHristov-sap]

New slot endContent is introduced in ui5-menu-item component. This slot accepts components that are displayed at the end of the Menu Item if it does not have sub-menu. If there are components slotted and also additionalText is being set, the additionalText will not be shown as well.

It is strongly recommended to slot only icon-only ui5-button, ui5-icon or ui5-link components.

BGSOFUIBALKAN-8160
#6350

[kgogov]

From the list item's side, the changes look fine to me.

[vladitasev]

This API looks a bit strange: you have 2 slots, but they are mutually exclusive, and also an additionalText property that is exclusive with the slots.

1. If you have passed submenu items, the "arrow" icon will be rendered
2. if you have passed end content, it will be displayed
3. lowest prio - the additionalText property will be displayed (this one is documented properly explaining that it's exclusive with the submenu)

There are 2 solutions:

• document the slots as mutually exclusive
• use the same "default" slot for both purposes: if you pass menu items, then work as before. But if you pass other content, act as the current "endContent". But maybe this is not ideal because what would happen if people pass a mix of submenus and arbitrary content? We'd still have to document how it would behave in that scenario. So maybe the current implementation is better

[NHristov-sap]

There are 2 solutions:

• document the slots as mutually exclusive
• use the same "default" slot for both purposes: if you pass menu items, then work as before. But if you pass other content, act as the current "endContent". But maybe this is not ideal because what would happen if people pass a mix of submenus and arbitrary content? We'd still have to document how it would behave in that scenario. So maybe the current implementation is better

Using one slot for all three purposes is not an option here, so I have updated the documentation to explain the priority of what is displayed at the end of the menu item.

[vladitasev]

There is a small typo ("nether" -> "neither") but it's ok to merge this change not to block progress on other menu changes.

We should consult with UA how to best describe this items > endContent > additionalText hierarchy and we can address this typo in this change.

[tsanislavgatev]

Looks good to me, but let's add UA to review the PR. We can merge it and address the coments later, but we can use this PR for the review