Reskillable Reimagined

- Fix for built in skills not updating the Attributes accordingly.

perk attributes in the json files can remain the old legacy style:

```json
{
"id": "swimming",
"displayName": "Swimming",
"enabled": true,
"perkAttribute": "forge:swim_speed",
"icon": "reskillable:textures/gui/custom_skills/swimming.png",
"perkOperation": "ADDITION",
"perkAmountPerStep": 0.1,
"perkStep": 5
}
```

Or if you want multiple perks you can rewrite the format like this:
```json
{
  "id": "swimming",
  "displayName": "Swimming",
  "enabled": true,
  "icon": "reskillable:textures/gui/custom_skills/swimming.png",

  "perkAttributes": [
    {
      "attribute": "forge:swim_speed",
      "operation": "ADDITION",
      "amountPerStep": 0.1,
      "perkStep": 5
    },
    {
      "attribute": "minecraft:generic.movement_speed",
      "operation": "MULTIPLY_BASE",
      "amountPerStep": 0.05,
      "perkStep": 10
    }
  ]
}
```