Timezone support

### The use case you're trying to solve
I use this action at JST, but expires time is shown as GMT only.
We need a feature to show it as other timezones.

### Change to the action that would solve that use case
Add a timezone option.
(And if it can, we also want a datetime format option.)

### Other considerations
none

No files or tests are named. Start by locating where the action declares inputs and formats the expiry time, then determine how a timezone option and the optional datetime format would be configured. Done means the action can display expiry times in a selected timezone, with the requested format behavior verified.

Written by the indexing model from the issue text.