Add Isp information to engines

[jesusrp98]

Add the isp tag to capsules' & rockets' info page.

In the case of Dragon capsules, it would be something like that:

"thrusters": [
  {
    "type": "Draco",
    "amount": 18,
    ...
    "isp": 235,
  }
]

And in the case of rockets, it'd include both sea level & vacuum Isp figures:

"engines": {
  "number": 9,
  "type": "merlin",
  "version": "1D+",
  ...
  "isp": {
    "sea_level": 282,
    "vacuum: 311
  }
}

[jakewmeyer]

Surprised that we missed that until now 😆

Added, just don't have hard numbers for sea level Draco and vacuum Super Draco at this point.

[jesusrp98]

I think we should just add the Isp that Wikipedia reflect about the Draco engines.
For Draco is 300s & SuperDraco has 235s of Isp.
Avoid adding a field like in the rocket endpoint, just add "isp": XXX. I think it would be easier to understand.

[jakewmeyer]

Updated

[jesusrp98]

Great, thanks for adding this!