Make graph data generic

[nathanpovo]

Fixes #196

This pull request adds the functionality to automatically infer the data format passed to the ForceGraph component with the use of TypeScript generics so that all ForceGraph functions/properties will automatically know the node and link data format.

[vasturiano]

Thanks for your PR @nathanpovo. Please see just a few comments.

[vasturiano]

Thanks for your work in this PR with the generic types @nathanpovo! Just merged, and will publish in a moment.

[huw]

This change is causing a TypeScript bug (microsoft/TypeScript#53287) for me when compiling. It’s not this repo’s fault, but the issue was that I was previously solving this problem by augmenting the package’s types:

declare module "react-force-graph-2d" {
  interface NodeObject extends VertexAttributes {
    id: string;
    x?: number;
    y?: number;
    fx?: number;
    fy?: number;
  }

  interface LinkObject extends EdgeAttributes {
    source: NodeObject;
    target: NodeObject;
  }
}

When importing a generic type from a package and augmenting it without supplying the parameters, TypeScript crashes completely. I don’t suspect too many users will be in my boat, but if they run into this issue hopefully they find this. The solution is just to migrate to the new generic types.