Inspired by solid work in #85, let's take the inserter dialog a bit further.

The model to emulate is an amalgam of Slack (when typing / in the message box) and the OSX Emoji inserter (invoke by pressing ^⌘ Space).

As soon as you invoke the inserter, you can use the arrow keys to pick a block and press enter to insert. If you start typing, you start filtering. Type ima and you'll probably narrow it down to an Image being the only block left. It has the focus rectangle, so when you press Enter, it's inserted.

To put it simply, if you're a keyboard shortcut person, you should be able to:

1. Type / on a new line to insert a block (see / on a newline should open the insertion dialog #24)
2. Type ima to filter down to just the Image
3. Press Enter to insert the image block