Embed Videos in Block Docs

To embed a video in Block Docs like this example, you can simply add a key called videos to block_data.json.

An full example with the videos key in it:

{
  "docstring": {
    "long_description": "The connection is made with the VISA address in the Flojoy UI.\nThis block should also work with compatible DS1000Z oscilloscopes",
    "short_description": "Connect Flojoy to a DS1074Z oscilloscope.",
    "parameters": [
      {
        "name": "device",
        "type": "VisaDevice",
        "description": "The VISA address to connect to."
      }
    ],
    "returns": [
      {
        "name": null,
        "type": "DataContainer",
        "description": "None"
      }
    ]
  },
  "videos": [
    {
      "title": "Digital Signals Oscilloscope",
      "source": "youtube",
      "link": "https://www.youtube.com/watch?v=0KqU-XWji9k"
    }
  ]
}

Currently only youtube is supported for the source key, and link is simply the YouTube link to the video. More video sources will be supported in the future.