the line editor supports custom keybinds and data storage, allowing for
a wide range of functionality to be implemented via plugins.
included plugins include:
* core: basic input and cursor movement.
* history: input history storage and retrieval (unfinished)
* highlight: support for colour-highlighting the line buffer (unfinished)
* syntax: parses the line buffer and uses `highlight` to apply syntax highlighting (unfinished).
* shell-integration:
- allows a `prompt` function to be defined, which will be called to get the text to
be used for the prompt
- exposes key properties of the line editor to the shell environment, allowing line editor
functionality to be extended via shell scripts.
