Pass the workspace_builder to plugin hooks instead of the tmux session

[hl037]

First of all, thank you for this app that changed my life with tmux !

In the current plugin system, it seems impossible to access the session configuration (from yaml or json).
Is there a specific reason the workspace is not passed in the hooks ?
...This would allow to easily extend the configuration file format.

I suggest to replace the session argument with a workspace_builder argument (which already gives access to the session) in the hooks. The drawback is that it's a breaking change. Here are some ways to overcome it:

• Duplicate the hooks
  • Have the new hook call the legacy one by default
  • Call both the hooks
• Add a new plugin class with hooks expecting the workspace builder

I can of course make a PR myself, but I need to know which way you prefer