Is it possible to include Nunjucks in a project with Composer?
Or do I have to download it manually?
No, you cannot install it via Composer, as it is a PHP dependency manager, used almost exclusively for PHP packages (which Nunjucks is obviously not). It's not impossible for non-PHP packages to be installable via Composer, but that's a rare occasion.
As a general rule of thumb, to check Composer availability - look at the source code repository and see if a file named composer.json
exists.
But that doesn't mean you have to download it by hand, as there's an equivalent solution for JavaScript packages - NPM; and Mozilla have made it available there.