Limelight Digital Bid Adapter: Add user sync

[imedvedko]

Type of change

• Bidder adapter related changes

Description of change

This PR adds user sync into limelight digital bid adapter

• test parameters for validating bids

var adUnits = [{
    code: 'placementCode',
    mediaTypes: {
        banner: {
            sizes: [[300, 250]]
        }
    },
    bids: [{
        bidder: 'limelightDigital',
        params: {
            host: 'exchange.ortb.net',
            adUnitId: 0,
            adUnitType: 'banner'
        }
    }]
}];

var videoAdUnit = [{
    code: 'video1',
    sizes: [[300, 250]],
    bids: [{
        bidder: 'limelightDigital',
        params: {
            host: 'exchange.ortb.net',
            adUnitId: 0,
            adUnitType: 'video'
        }
    }]
}];

• contact email of the adapter’s maintainer engineering@project-limelight.com
• official adapter submission

[musikele]

LGTM