Performax adapter

[VasekProchazka]

Type of change

• New bidder adapter

Description of change

Add a new bidder adapter for Performax

• test parameters for validating bids

{
  bidder: '<bidder name>',
  params: {
    slotId: "28"
  }
}

• contact email of the adapter’s maintainer: development@performax.cz
• official adapter submission

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/

[VasekProchazka]

Docs PR prebid/prebid.github.io#2123

[FilipStamenkovic]

All in all, MR looks ok, you just need to fix lint errors you have. Take a look at the circleci output on this PR (basically you just need to replace " with ' in your test file).

I also added recommendation to remove unused functions.