[Bug] time-picker keyboard input does not respect date value

[RS-Sautter]

Vue2-datepicker version: 3.8.1
Vue version: 2.6.12
Browser: Chrome 86

Steps to reproduce

1. Set value for vue2-datepicker to now + 1day
2. Set type to "time"
3. Set disabled-date e.g. to: (date) => date < new Date()
4. Now you can select a time value in the dropdown which is lower than the current time
5. Bug: You cannot type in a time < now

Expected behavior
You also can type in a time value < now, because it is for tomorrow.

Actual behavior
It gets corrected to the previous value that was set.

Underlying Problem
In l.242 of src/date-picker.js the backupTime is set to new Date().
This means that it tries to construct a date from your time input + the other values (year, month, day) of new Date(). This leads to the conflict with the disabled-date function.

[RS-Sautter]

#561