Fix endOf bug when day light saving interferes with it

[sazary]

Description:

endOf has bug when it's used to get end of week for 2020-03-21 until 2020-03-27.

Steps To Reproduce:

Run this code snippet:

moment('2020-03-21 07:10:20').endOf('week')

Expected value: 2020-03-27
What it returns: 2020-03-28

Notes About Code

Please note that I've largely copied contents of endOf function from moment lib itself. Specifically, please see this switch.
I've tried to stick to code conventions of this repo, but if there's any problem please let me know.

[behrang]

I didn't put enough time to check this, however in the code, endOf is implemented in terms of startOf, which only checks for jmonth and jyear, and all other values are passed back to moment itself.

I checked some values:

moment('2020-03-19', 'YYYY-MM-DD').endOf('week').format() // 2020-03-21T23:59:59+04:30
moment('2020-03-20', 'YYYY-MM-DD').endOf('week').format() // 2020-03-21T23:59:59+04:30

moment('2020-03-21', 'YYYY-MM-DD').endOf('week').format() // 2020-03-22T00:59:59+04:30

moment('2020-03-22', 'YYYY-MM-DD').endOf('week').format() // 2020-03-28T23:59:59+04:30
moment('2020-03-23', 'YYYY-MM-DD').endOf('week').format() // 2020-03-28T23:59:59+04:30

The first two and the last two are correct by my calculations. However, the middle one is wrong, since that hour does not exist. Maybe we can fix that.

I don't get the reason for your code. Can you explain more?