Quickfix: select copyEl before copying text

[garrettr]

This is a quickfix for #29. I'm fine with merging this for now, but also think the technique of adding the share text as a hidden input element and using document.execCommand('copy') is a bit of a hack, and there might be a cleaner way to do this using Electron's Clipboard API.

@GabeIsman Did you try using Electron's Clipboard API at any point while implementing this feature? Wondering if there's some reason why it wouldn't work (obviously I am fairly novice when it comes to both Electron and React).

[GabeIsman]

I can't remember exactly what the reasoning was, but I think the Electron API was still marked experimental at the time, and I was thinking that a pure web-technologies solution would be more stable. Although somehow it broke anyway. I don't see anything wrong with using the Clipboard API, except that the integration tests will need to be modified.

[garrettr]

I can't remember exactly what the reasoning was, but I think the Electron API was still marked experimental at the time

Sounds reasonable. FWIW, some of the Electron Clipboard API methods are still marked experimental as of Electron 1.6.10, but the only one we need, writeText, is not one of them.