ModalSheet appears too high on the screen

[shyunMin]

Describe the bug
ModalSheet appears too high on the screen

To Reproduce
Steps to reproduce the behavior:

1. Launch Meterial Gallery
2. Select MModalBottomSheets Gallery
3. Click OPEN MMODALBOTTOMSHEETS button

Screenshots

[shyunMin]

The reason why MModalSheet appears in the wrong position of the screen is the ratio value is fixed to 0.5 regardless of content size.

Tizen.NET.MaterialComponents/src/Tizen.NET.MaterialComponents/Components/MModalSheets.cs

Line 8 in a768a7e

double _bottomSheetDefaultRatio = 0.5;

This issue cannot be solved, because there is not way to get content size before the MModalSheet is appeared without changes of MModalSheet's structure