nexx360 Bid Adapter : add support for video

[gchicoye]

Type of change

• Bugfix
• Feature
• New bidder adapter
• Code style update (formatting, local variables)
• Refactoring (no functional changes, no api changes)
• Build related changes
• CI related changes
• Does this change affect user-facing APIs or examples documented on http://prebid.org?
• Other

Description of change

We've added video support to our bidder

• test parameters for validating bids

{
         bidder: 'nexx360',
         params: {
            account: '1067',
            tagId: 'luvxjvgn'
         }
}

For any changes that affect user-facing APIs or example code documented on http://prebid.org, please provide:

• A link to a PR on the docs repo at https://github.com/prebid/prebid.github.io/ :
• Nexx360 - Video added to nexx360 bid adapter prebid.github.io#3686