Kubient bid adapter. Added video support and honoring v5 requirements

[onaydenov]

Type of change

• [ x] Bugfix
• [ x] 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?
• [x ] Other

Description of change

Added fixes for issues:
#6512
#6466
#6465
Added Video support
New PBJS endpoint
Compliant to Prebid v5

Documentation update:
prebid/prebid.github.io#3043

• test parameters for validating bids

Banner:
var adUnits = [
    {
        code: 'banner-ad-unit',
        mediaTypes: {
            banner: {
                sizes: [[300, 100]]
            }
        },
        bids: [{
            bidder: 'kubient',
            params: {
                zoneid: "5fbb948f1e22b",
            }
        }]
    }
];

Video:
var adUnits = [
    {
        code: 'video-ad-unit',
        mediaTypes: {
            video: {
                playerSize: [300, 250],               // required
                context: 'instream',                  // required
                mimes: ['video/mp4','video/x-flv'],   // required
                protocols: [ 2, 3 ],                  // required, set at least 1 value in array
                placement: 1,                         // optional, defaults to 2 when context = outstream
                api: [ 1, 2 ],                        // optional
                skip: 0,                              // optional
                minduration: 5,                       // optional
                maxduration: 30,                      // optional
                playbackmethod: [1,3],                // optional
                battr: [ 13, 14 ],                    // optional
                linearity: 1,                         // optional
                minbitrate: 10,                       // optional
                maxbitrate: 10                        // optional
            }
        },
        bids: [{
            bidder: 'kubient',
            params: {
                zoneid: "60ad1c0b35864",
            }
        }]
    }
];

• contact email of the adapter’s maintainer oleg.naydenov@kubient.com or prebid@kubient.com
• [x ] official adapter submission
• A link to a PR on the docs repo Kubient adapter. Add video support prebid.github.io#3043

Other information

[onaydenov]

we'll re-open after spec is amended