kanata configuration for sticky modifier keys

gistfile1.txt

One can use https://github.com/jtroo/kanata to remap or modify keyboard keys.
What follows is a configuration to make the modifier keys sticky. 
The modifier keys are: Control keys, Shift keys, Alt keys, WinKey/Super/Meta key, Caps Lock.
They now work in two ways:
- As before one can hold down modifier keys, and tap other keys, to get e.g. Ctrl-a
- One can now also just tap modifier keys, followed by tapping an ordinary key.
  - There is a timeout for how long the tap of a modifier key is valid, here configured to two seconds.
  - Tapping the WinKey/Super/Meta key is usually handled specially in e.g. Ubuntu. This functionality is not lost, but is
    delayed until the timeout.
    
Motivation: I do not have RSI problems. I just think that it is convenient, and more ergonomic, to be able to use
sticky modifier keys, while also having the old (conventional) functionality available.    

I used kanata 1.10.0-prerelease-2, in Ubuntu 25.04.
Here is the config, without comments, to keep it brief. To understand the configuration better, one can have a look at the
documentation and sample configurations in the github kanata repo.
```
(defcfg
 process-unmapped-keys yes
)

(defvar
 os-timeout 2000
)

(defalias
  oslctl (one-shot $os-timeout lctl)
  osrctl (one-shot $os-timeout rctl)
  oscaps (one-shot $os-timeout caps)
  oslmet (one-shot $os-timeout lmet)
  oslalt (one-shot $os-timeout lalt)
  osralt (one-shot $os-timeout ralt)
  oslsft (one-shot $os-timeout lsft)
  osrsft (one-shot $os-timeout rsft)
)

(defsrc
  lctl rctl caps lmet lalt ralt lsft rsft
)

(deflayer default
  @oslctl @osrctl @oscaps @oslmet @oslalt @osralt @oslsft @osrsft
)

```