Missing rounded corners in <ui5-popover>

[pavelkornev]

Describe the bug
On https://sap.github.io/ui5-webcomponents/playground.html#/components/Popover
When opening the popover, the top corners are rounded and the bottom not:

I assume it might be a design decision to round only top corners, but it doesn't look so because in such scenarios the contrast is normally higher (e.g. 3-5 time bigger border-radius, example — https://i.stack.imgur.com/srHXl.png).

Expected behavior
all 4 corners should be rounded or not, or have an explicit contrast.

[pavelkornev]

And there is also the accessibility issue in this example (click on label doesn't bring focus on the field):

[ilhan007]

Hello @pavelkornev.

The accessibility issue is addressed with
#33

And, regarding the rounding of the popover corners, we will raise the question to the designers and get back to you.

[ilhan007]

Hello @pavelkornev, we rounded the bottom borders.