Add example payloads to readme

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List supported question types and write up possible JSON for each type

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some example form_content.content to start off:

{
    "type": "radio",
    "prompt": "who was first president?",
    "weight": 1,
    "shuffle": true,
    "opt": {
        "tony tuna": 0,
        "jen jameson": 0,
        "april summer": 0,
        "george": 1
    }
}

{
    "type": "radio",
    "path": {
        "type": "key",
        "case": "tony tuna"
    },
    "prompt": "why did you choose tony tuna?",
    "weight": 0,
    "shuffle": true,
    "opt": {
        "I dunno": 0,
        "just dumb i guess": 0,
        "i love tuna": 0
    }
}

the 'path' element works in sequenced forms only. Bridges should JS show/hide elements based on the 'key' or 'score' of preceding elements.

{
    "type": "radio",
    "prompt": "whats your favorite color?",
    "weight": 0,
    "shuffle": false,
    "opt": {
        "charcoal": 0,
        "cyan": 0,
        "chartreuse": 0,
        "coral": 0
    }
}

{
    "type": "tick",
    "prompt": "days of week?",
    "weight": 1,
    "shuffle": true,
    "scoring": "all",
    "opt": {
        "monday": 1,
        "funday": 0,
        "cervesa": 0,
        "saturday": 1
    }
}

{
    "type": "text",
    "prompt": "final comments:",
    "weight": 0
}