Add border or shadows to annotation modal window

Using the default theme included in 3.4 M1, there is a lot of white/bright colors that are very close to each other, making hard for the end-user to distinguish them.

I would like to propose adding one of the following two:

• a border in the same style that we have for the Add submeniu
• a shadow to the annotation modal, so users can easily see the size of the window

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