[Example]: Use serde, schemars to make structure output code easy

[cptrodgers]

Use serde and schemars to write structure output example.

[cptrodgers]

Tested in local:

[cptrodgers]

Relating issue: #302

[cptrodgers]

   Compiling structured-outputs-schemars v0.1.0 (/Users/rodgers/Working/async-openai/examples/structured-outputs-schemars)
    Finished `dev` profile [unoptimized + debuginfo] target(s) in 11.74s
     Running `/Users/rodgers/Working/async-openai/target/debug/structured-outputs-schemars`
{
  "final_answer": "x = -3.75",
  "steps": [
    {
      "output": "8x + 7 = -23",
      "explanation": "Start with the equation: 8x + 7 = -23."
    },
    {
      "output": "8x = -23 - 7",
      "explanation": "Subtract 7 from both sides to isolate the term with x."
    },
    {
      "output": "8x = -30",
      "explanation": "Calculate the right side: -23 - 7 = -30."
    },
    {
      "output": "x = -30 / 8",
      "explanation": "Now, divide both sides by 8 to solve for x."
    },
    {
      "output": "x = -3.75",
      "explanation": "Simplify -30 / 8 to find the value of x."
    }
  ]
}

Re-run to check example result.

[64bit]

Thanks, looks good!