[Donate Button] Verify the Donate button and the modal window with the donation options appear according to mockup and requirements

**Priority: high**

**Description:**
Test case verifies if the Donate button and the modal window with the donation options will appear according to mockup and requirements

**Preconditions**
1. Go to “StreetCode” page

**Steps to reproduce**
1. Verify if the Donate button is displayed and pinned to the bottom right corner of the screen.
2. Verify if the Donate button is displayed on a white background.

3. Verify if after hovering over the Donate button, a shadow appears behind the button.
4. Verify if after clicking the Donate button a modal window with donate options opens.

6. Verify that clicking on the grey place or the X button (on the desktop version) closes a modal window.

**Expected result**
The Donate button and the modal window with the donation options will appear according to mockup and requirements

**User story: #78 , #136**
**Test Case: #340**