Add Event hooks to Plugins

Is your feature request related to a problem? Please describe.
There aren't any ways to initialize plugins. Reading Settings and other tasks have to be done in the actions that they are relevant for.

Describe the solution you'd like
Methods to handle LifeCycle hooks of the Plugin such as OnLoad, OnUnload, OnReload...etc, as well as event callbacks of the Application which could include: OnWorkspaceOpen or more granular events: OnDocumentOpen, OnCollectionOpen

Describe alternatives you've considered
Running code when the file is executed is easy and certainly possible but it lacks access to the Insomnia plugin context. e.g no saving to the store to read later or alerting the user to changes in a new version.

Additional context
Related to #2599 which would be another useful hook