Add Dvorak layout

[vinc]

Hello, I started coding a toy OS and your crate is really helpful, thanks!

I use a Dvorak layout so I created one by copying the US 104 layout and keeping only the diff, like the code of the UK 105 layout does.

I didn't change any of the ctrl modifiers, not sure if I should? I don't use that on my keyboards so I don't really know.

[thejpster]

So the deal with Control + Key is that Control + A gives 1 (0x01), Control + B gives 2 (0x02), and Control + Z gives 26 (0x1A).

I think following the principle of Least Surprise would mean that Control + C would do a 'Copy' function, no matter where on the keyboard the 'C' key was. I therefore propose we change the Dvorak mapping so that Control + Letter gives the correct control code for the letter printed on the key, as opposed to the letter at the corresponding position on the US keyboard (i.e. the KeyCode).

[thejpster]

This diff also highlights the issue with naming the KeyCode letter keys after the letter they have on a US keyboard, but I can't think of anything better to use - mapping Key R to Unicode character P seems marginally less confusing than mapping Key 19 to P.

[vinc]

Thanks, I'll change the Control modifiers, it's indeed much better!

For the KeyCode naming I think it's good as it is, personally I didn't think it confusing because my keyboards are either blank or azerty, so I'm used to having a mental image of a physical US keyboard then remapping it to the actual output I want.

[vinc]

I changed the modifiers so that pressing CTRL with the key that produce a C for example will result in CTRL+C as expected. And while I was doing that I noticed that you are using is_caps() for upper-case letters and is_shifted for symbols, so I did the same.

[thejpster]

Thank you so much!