Make facebook config type properties optional

[samcarton]

Fix for the below issue when using react-player facebook config in typescript

Current Behavior

• Using react-player with typescript
• when trying to pass facebook config the type definitions require all config fields.
• Typescript flags it as an error if you just try to pass one prop e.g. appId.

Expected Behavior

Should be able to configure as per the sample in the docs:

<ReactPlayer
  url={url}
  config={{
    youtube: {
      playerVars: { showinfo: 1 }
    },
    facebook: {
      appId: '12345'
    }
  }}
/>