Support copying and pasting text on phone

最近常使用手機做筆記，但是發現HackMD不支援手機的複製及貼上功能
如果有的話使用會更加順手， 謝謝您！
我用的是iphone7(版本 10.1.1)

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I usually make notes on HackMD with phone recently , but it doesn't support copying and pasting with phone.If the function could be added , it would be very nice!
I use iphone7(version 10.1.1).

best wishes.

Start by reproducing the copy-and-paste problem on the stated iPhone 7 and iOS 10.1.1 environment, then trace the phone editing behavior in the application. Done means users can copy and paste text reliably while editing notes on a phone.

索引モデルが issue の本文から書いたものです。