EXADS Bid Adapter: initial release (prebid#11284)

* First commit

* fix: readme.md

* fix: changed exads urls

* fix: Tools and suggestions related to the doc

* fix: from code review

* fix: from code review

* fix: from code review

* fix: error from code review - native example

* fox: from code review

* fix: from code review

* fix: from code review

* fix: native img set as mandatory

* fix: from code review

* fix: from code review

* fix: from code review

* fix: from code review

* fix: from code review

* fix: from code review

* fix: bidfloor and bidfloorcur set as optional

* fix: dsa

* fix: mananing multiple responses

* fix: unit test after code review

* fix: fixing native snippet code

* fix: from code review

* fix: video events after code review

* fix: video module into documentation

* fix: impression tracker for native

* fix: afeter code review

* fix: unit tests

* fix: added badv and bcat

* fix: video -> mimes and protocols

* fix

* fix: removed image_output and video_output params, forcing always html for rtb banner

* fix: gulp

* fix: added site.name

* fix: removed EXADS dir

* fix: after linting

* fix: unit tests

* fix: final dsa solution

* fix: dsa

* fix: fix instream example

* fix: doc media type context

* fix: documented the endpoint param into native section

* fix: related to markdown lint validation (#2)

* fix: from CR (#3)

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Co-authored-by: tfoliveira <tfoliveira@users.noreply.github.com>

Author: giuseppe-exads