Update header image for BOLT.FUN site

Update the BOLT.FUN website (bolt.fun) header image to match the new branding. You can find the files here:

https://www.figma.com/file/SrwhugoFalEyB8TKhBMLIw/Shock-the-Web?node-id=424%3A1684

Zip-file here:

[header-img.zip](https://github.com/peakshift/bolt.fun/files/8216044/header-img.zip)

