Add option to force ghost install

Summary

As a security precaution, ghost cannot be installed in a non-empty directory. This behavior is detrimental in at least one case. Consider a system utilizing nodeenv to manage multiple versions of NodeJS. If the system’s global NodeJS version is set to 14.x, ghost cannot be installed due to version incompatibility. Creating a new directory for ghost and setting the local (directory) NodeJS version to 12.x via nodeenv creates a folder named env, which then blocks ghost from installing due to a non-empty directory.

Proposed solution is to add a --force flag to ghost install.

[acburdine]

@bermudalocket that approach makes sense - I’ll work on adding that 👍

[bermudalocket]

As an end user unfamiliar with the inner workings of this project the semantics of the flag makes no difference to me. If there’s a choice that better adapts to an existing naming scheme then that is obviously the better choice.