EconomyManager is a simple class that allows developers to add economy support into their plugins. It currently comes in one variant, but there is one more planned.
To use EconomyManager, simple copy the file into your project, and load up a new constructor of EconomyManager in the class you wish to access economy from. There is no need to place special dependencies in your Plugin annotation, EconomyManager just works. The methods available to developers are self-explanatory.
What you could do is offer this, and then when the official Economy API, change all the code (leaving method names the same) to be compatible with the official API so plugins using it as a dependency can either just update their version of this, or server owners can update the plugin version.