impr(custom theme rename modal): automatically select input (@fehmer)

[fehmer]

Select the name text input on the Update custom theme modal so the user can directly type in the new name without deleting the old one

[fehmer]

Make this option available on simple modals:

monkeytype/frontend/src/ts/utils/animated-modal.ts

Line 176 in 120b660

focusFirstInput(setting: true | "focusAndSelect" | undefined): void {

[Miodec]

Thanks