ISO third level keys were not working. That prevented some inputting
important characters (like pipe `|` and caret `^`) on some keyboard
layouts.
Instead of parsing the user-agent string to find the users os, we now
look into the `platform` attribute of the `navigator` object.
Removed the hijacking of the command key `⌘` on Mac OS as the `Alt` key
on other systems.
Many systems (including MS Windows and many linuxes) map `<Ctrl>` +
`<Insert>` to copy and `<Shift> + <Insert>` to paste. That serves as a
handy fallback when the more common `<Ctrl> + C` and `<Ctrl> + V`
keybindings have their default prevented to send signals to the
terminal.
Currently all keydown-events with the insert key send `\x1b[2~` to the
terminal. This commit won't send that key if either the `shiftKey` or
the `ctrlKey` are present. Instead it will enable `contentEditable` to
allow for pasting.
runarberg