fix horizontal loading spinner jump

[mattg95]

The loading spinner causes the title to jump horizontally when it appears. This is due to the fact that an extra element is being rendered into the flex box. This PR adds a style to the loading spinner that does not cause the title to jump when the loading spinner is rendered

Issue:

https://github.com/wix/react-native-calendars/assets/45606434/88793fa2-ce67-43a5-986c-33d2ab398fb2

Fix:

https://github.com/wix/react-native-calendars/assets/45606434/9b8bca6d-4a99-445d-9b42-b3c4d7e6fd80

[stale[bot]]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.