Simple Entity Inspect hotkey

## What problem does this solve or what need does it fill?

While we're waiting on the inspector, something that could be implemented in just a few lines of code is an entity inspection hotkey.

## What solution would you like?

A plugin which, when added, would register a global hotkey (something like ctrl/command-shift-I for "inspect). This would take whatever entity the mouse is currently hovering over, and call `inspect()` on it, printing it to the console. Whether this should print all children is TBD - perhaps the `alt` key could select between hierarchical and non-hierarchical readouts.

Note that it would be the user's responsibility to ensure that the appropriate picking backends were installed - normally only the UI backend is enabled, and if you wanted to use this to inspect 3d models, you'd need to install one of the 3d backends (either raycast or physics).