Show password (eye icon). Nonintuitive functionality.

[JohnGurin]

It shows the password when you hold the touch on the icon.
It would be more convenient that the icon switches the password visibility. So it would be easier to enter a password.

[Jonny Buchanan]

For the "good first issue" tag, this needs to be changed to toggle showPassword using onTap instead:

https://github.com/insin/vlc_remote/blob/240549ccfa798eabec467fa7c0d896433eaefb2b/lib/settings_screen.dart#L239-L248

[Jonny Buchanan]

Fixed in #10