Create collectcent.md (prebid#1055)

Collectcent bidder adapter documentation

Author: devcollectcent

dev-docs/bidders/collectcent.md

@@ -0,0 +1,19 @@
+---
+layout: bidder
+title: Collectcent
+description: Prebid Collectcent Bidder Adaptor
+top_nav_section: dev_docs
+nav_section: reference
+hide: true
+biddercode: collectcent
+biddercode_longer_than_12: false
+prebid_1_0_supported : true
+---
+
+### bid params
+
+{: .table .table-bordered .table-striped }
+| Name           | Scope      | Description                                                    | Example            |type|
+| :-----------   | :--------- | :------------                                                  | :----------------- |:---|
+| `placementId` | required   | Placement Id will be generated on Collectcent Platform. | 0                        |integer|
+| `traffic`      | optional   | Type traffic                                             | 'banner'                 |string|