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.