EXADS Bid Adapter: initial release (prebid#5237)

* feat: added exadsadserver.md for PR purposes

* fix: after code review

* fix: changed main parameters

* fix: from code review

* fix: clear names

* fix: related to markdown lint validation (#3)

* EX-21135 - from CR (#5)

* fix: related to markdown lint validation

* fix: from code review

* fix: from code review

* EX-21135 - from CR - making URL as relative (#6)

* fix: related to markdown lint validation

* fix: from code review

* fix: from code review

* fix: from CR

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Co-authored-by: Pierre Brouca <[email protected]>