Remap rshift

Hey,

I try to remap the `rshift` key, because the macbook has awful small `arrow up` and `arrow down` keys. I want to remap `rshift` with `arrow up` and `arrow up` with `arrow down`. I never used the `rshift` key anyway, so why not remap it and get a bigger keypad.

I tried

```
rshift : skhd -k "up"
```

and

```
0x3C : skhd -k "up"
```

The first one just results in `#5:10 expected '-'`. The second one in nothing. Is `0x3C` even the correct key code? `skhd -o` shows it when I press `rshift`.

Start by reproducing the two configurations from the issue and use `skhd -o` to verify the reported right-shift key code. The payload names no source file or test, so locate the key parsing and remapping entry points before determining how the requested key swaps should be represented and verified.

Written by the indexing model from the issue text.