Devadex already indexes your product from public data. Claim it to correct the details, and to set a custom affiliate rate so Devadex features you above the default.
Verification token:
Add that exact text anywhere on your product page (the description works), save, then:
Verified — you own . Update anything below.
Set the actual rate in your Gumroad dashboard by adding Devadex as an affiliate with this percentage. Recording it here lets Devadex feature your listing.