There is no specific plugin for this so you need to follow google Adsense indications and:
a) Use the custom headers plugin: Inject the Adsense’s JS there (easiest and fastest way).
b) Create a theme: Create a subtheme dnd inject the Adsense’s javascripts in your html header.
c) Develop a plugin: The hard and slow one… but the best if you like to share your work with the PKP community.
As you expect, I will recommend you go with (a) and just add Adsense JS to your header.
The only but if you operate with EU citizens is that you will need to be sure Adsense won’t keep their IPs. Not sure about this service but in googleAnalytics they include a tag to anonimize the tracking.
Cheers,
m.