Add taboola bid adapter

[mikizi]

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

• test parameters for validating bids

{
  bidder: 'taboola',
  params: {
          tagId: 'test-1',
          publisherId: 'test',
          bidfloor: 0.25, // optional default is null
          bidfloorcur: 'USD', // optional default is USD
          bcat: ['IAB1-1'], // optional default is []
          badv: ['example.com']  // optional default is []
     }
}

Be sure to test the integration with your adserver using the Hello World sample page.

• contact email of the adapter’s maintainer : prebid@taboola.com
• 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/
• Here will be the link for the docs of Taboola new bidder (need to be done by peter)