Compile combdownloader-ng

TL;DR:

git clone https://codeberg.org/watashi564/combdownloader-ng.git
cd combdownloader-ng
go mod init localhost/combdownloader
go mod tidy
go build
cd ..

Note: This will not recreate the reproducible binary on the downloads page. To get exactly the same binary as the one on the downloads page, you need to use the Dockerfile found in the repoducible repo on codeberg.