Fix FunctionDeclarationSchema type not allowing strings

[hapticdata]

If I use Google's AI Studio and edit my functions. It will give me an object like this:

[
  {
    "name": "getWeather",
    "description": "get the weather for a location",
    "parameters": {
      "type": "object",
      "properties": {
        "location": {
          "type": "string"
        }
      }
    }
  }
]

TypeScript will throw an error for this because I used "object" instead of SchemaType.OBJECT for "type". It will however work fine in Javascript.

This pull request simply allows FunctionDeclarationSchema to accept any value from the SchemaType enum or its string equivalent.

type: "string" | "number" | "boolean" | "object" | SchemaType | "integer" | "array"