smartx Bid Adapter: add support for sitekey (prebid#4265)

* initial commit

* adjustments

* adjustments

* adjustments

* typo, further adjustments

* removed userIds and schain support

* Added optionals to outstream and made formatting

* Update smartx.md

minor edits for clarification and readability.

* adjusted outstream_options

* remove outstream_function, added pbjs_version_notes

* bugfix outstream options for default outstream renderer configuration

* refactor descriptions and adding "visibilityThreshold"

* Add schain support

* add support for sitekey to smartxBidAdapter

---------

Co-authored-by: Gino <[email protected]>
Co-authored-by: Jean Stemp <[email protected]>
Co-authored-by: smartclip-adtech <[email protected]>

Author: 3 people

dev-docs/bidders/smartx.md

@@ -35,6 +35,7 @@ Please reach out to your smartclip business contact for any questions and assist
 | `price_floor`        | optional | Set the current channel price floor in real time.                                                       | `10`                    | `integer`   |
 | `min_duration`       | optional | Minimum video ad duration in seconds                                                                    | `15`                    | `integer`   |
 | `max_duration`       | optional | Maximum video ad duration in seconds                                                                    | `60`                    | `integer`   |
+| `sitekey`            | optional | Sitekey provided by smartclip.                                                                          | `'foo.bar.baz'`           | `string`    |
 
 <a name="smartx-outstream-options-object" />