Add this jar to the modules/platform directory and you should be good to go.
Tested on Alfresco 5.1.
The jar just contains a webfragment.xml that configures the com.thetransactioncompany.cors.CORSFilter available in the classpath.
I recommend checking out api-explorer.alfresco.com and the source is here.
The Api Explorer makes use of Open Api (aka Swagger) definitions. If you would like these definitions within the Alfresco.war (perhaps to support custom tooling) then checkout the withdev branch of this project.
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This file is part of an unsupported extension to Alfresco.
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