Add open collective banner information

[TheLarkInn]

Open Collective has a nice document for how to add our open collective banner information to the webpage.

This would probably just live in the bottom of the landing page for now. If we would like to experiment with different badges or things in like the header or footer we could do so, but for now I would just like to have the banner there for visibility as we are getting very close to finishing our milestone.

[TheLarkInn]

Looking into this further the script is probably not best suited for our needs. Rather, we should use the html inside that is being used.

          <h1>This is possible thanks to you</h1>
          <h2>This project is possible thanks to our backers and sponsors</h2>
          <object type="image/svg+xml" data="https://opencollective.com/webpack/sponsors.svg"></object><br />
          <object type="image/svg+xml" data="https://opencollective.com/webpack/backers.svg"></object>

[SpaceK33z]

I agree with your last comment, less external scripts = better :).

[bebraw]

Merged the PR, closing.