Initials font-size does not change if the avatar size changes dynamically

[zhaoqixu]

The initials font-size works as expected at the time the avatar is firstly created and mounted to the DOM tree. However, later when we change the avatar size dynamically and pass the updated size as props to the avatar component, the overall avatar size changes as expected but the initials font-size remains the same.

The ability to adjust the intials size dynamically is important for scenarios like video conferencing where the avatar size could change depending on the number of people joining or leaving the group.