composer require "flarum/flarum-ext-embed":"dev-master"
Your requirements could not be resolved to an installable set of packages.
- Installation request for flarum/flarum-ext-embed dev-master -> satisfiable by flarum/flarum-ext-embed[dev-master].
- flarum/flarum-ext-embed dev-master requires flarum/core 0.1.0-beta.8 -> satisfiable by flarum/core[0.1.x-dev] but these conflict with your requirements or minimum-stability.
Installation failed, reverting ./composer.json to its original content.