Implementing alias token manipulation in design-tokens-library

[Pukimaa]

Currently it seems like while alias tokens according to spec is implemented, however it'd be nice to be able to manipulate those, which is possible in design tools like Penpot. It works by appending an alpha hex value to the end like so:

"subtle": {
      "$value": "{neutral.900}14",
      "$type": "color",
      "$description": ""
}

Where {neutral.900} resolves to a 6-digit or 8-digit hexcode, and 14 is the hex code for 8% and should either append it to the 6-digit hexcode or replace the last two letters in the 8-digit hexcode.

This would be a very welcome QoL feature and might be something implemented into the spec itself soon too.