Add tests for select

[Kzoeps]

1. Created a test to check if select is rendered
2. Created a test to see if the initial value is set on render. Did this using a check to see if the selected value is initially present or not. Couldn't use value since antd renders Select as input with combobox and doesn't update the value
3. Created a test to see if the value changes when the user clicks on a different option. Since fireEvent.change does not seem to work, I used mouseDown to first open the select and then click to select an option. antd renders the options as span so I was not able to use option.selected. Furthermore I used the check of toBeGreaterThan since I couldnt find a way to close the dropdown.

@jannikbuschke lmk what if you have any feedback or changes to be made

Referenced these links while coming up with the third test:

1. Impossible to expand Select component dropdown programatically ant-design/ant-design#22074 (comment)
2. Cannot test Select with react testing library after upgrading to v4 ant-design/ant-design#23009

[jannikbuschke]

looks cool 👍
@all-contributors add @Kzoeps for test

[allcontributors]

@jannikbuschke

I've put up a pull request to add @Kzoeps! 🎉