Add a recharge field to features and other applicable elements

Many abilities in the game can only be cast a certain amount of times until they are recharged. A few examples, not all are SRD compliant but there is no detailed info here :
* bardic-inspiration-1 : Charisma times per long rest
* font-of-inspiration : transforms the long rest in short rest for the bardic inspirations
* wand of magic missiles : 7 charges, 1d6+1 recharge per long rest
* ki : level times per short rest
* Druid Star Map: Guiding bolt : proficiency times per long rest
* Githzerai psionics : Either Shield or Detect through 1 times per long rest

It would be great to have a way to represent the amount of times a feature or one of its element can be used. For example on "ki":
```json
{
"index": "ki",
...
"resources": [ {
"name": "Ki Point",
"dependency": {
"name": "ki",
"url": "...."
},
"amount": "${level}",
"amount": "min(1, ${charisma})", // Example of a representation of something that could be parsed and evaluated
"recharge": "short-rest",
"recharge_amount": "full",
"action": "various"
}]
}
```

Having such a representation would help building automated resource management summaries, with checkboxes or textfield to activate or reduce the available amount of resource of a particular ability.

The current workaround would be to parse the "desc" field and hope we have guessed the right information.

Look at the existing feature data structures in the repository, likely in a data directory. Understand how resources are currently represented. The issue suggests adding a 'resources' array with fields like name, dependency, amount, recharge, recharge_amount, and action. Start by examining a sample feature file (like for 'ki') to see the current schema. Determine where to add this new field and how to parse expressions like '${level}'. Check if there are existing tests for data validation.

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