Add `--offline` mode that disables all network features at runtime

Add --offline mode that disables all network features at runtime: One thing I have found in the past with editors focusing on collaboration and connectivity is that they are very frustrating to use when network connectivity is bad or non-existent. They throw error after error about not being able to check for plugin updates and not being able to sync files and not being able to open chat and whatever else. The more connected the editor is the more frustrating it tends to be to use in local only mode when the circumstances call for it.