Add a landing page

[claudioantonio]

Instead of creating a website for Bugless, a good enough solution to continue moving forward and don't spend energy with it yet would be to add a Hero page where the user could have some brief description, a link for the README file and also did not face directly the list of bounties, which in a first moment will be kind of empty (with only the solidity compiler bounty).

One proposal for the hero page is presented below. The "Explore Bounties" button will direct users to the list of existing bounties and the "Learn More" link will move users to the README file on the github repo. The text in the image is only a suggestion and can changed at will.

[guidanoli]

Would be nice to have some (AI) art as eye candy. :-)