Export IWithData and IWithForm types

[jdforsythe]

Fixes #63

Exports IWithData and IWithForm types
Explicitly makes generic extend IOptionsBase
Changes IWithData's data property to be string, Buffer, or object (allows strings, Buffers, objects, or arrays)

No behavior is affected so no new tests were written

Example usage - you can now construct a typed options object using the IWithData or IWithForm types.

import * as phin from 'phin';

export const app = async () => {
  const stringOpts: phin.IWithData<phin.IOptions> = {
    url: 'http://localhost:8008',
    parse: 'none',
    data: '1',
  };

  const bufferOpts: phin.IWithData<phin.IOptions> = {
    url: 'http://localhost:8008',
    parse: 'none',
    data: Buffer.from('1'),
  };

  const objectOpts: phin.IWithData<phin.IOptions> = {
    url: 'http://localhost:8008',
    parse: 'none',
    data: { val: 1 },
  };

  const arrayOpts: phin.IWithData<phin.IOptions> = {
    url: 'http://localhost:8008',
    parse: 'none',
    data: [{ val: 1 }],
  };

  const res1 = await phin(stringOpts);
  const res2 = await phin(bufferOpts);
  const res3 = await phin(objectOpts);
  const res4 = await phin(arrayOpts);

  console.log(res1.body);
  console.log(res2.body);
  console.log(res3.body);
  console.log(res4.body);
};

If you think something should be added to documentation, let me know.

[ethanent]

Thank you very much.