knitr engine for {rpic} chunks

Register with rpic_register_knitr(), then write pic code in a chunk:

```{rpic, circuits=TRUE}
A:(0,0); B:(2,0)
resistor(A,B)
```

Chunk options: circuits, texlabels, scale.

Usage

rpic_knitr_engine(options)

Arguments

options

knitr chunk options.

Value

The chunk output produced by knitr::engine_output() (the rendered diagram as an included figure).