add doc for quarto-dev/quarto-cli/pulls/11000

Author: cscheid

docs/extensions/lua-api.qmd

@@ -247,4 +247,12 @@ Quarto includes a copy of [lbase64](https://github.com/iskolbin/lbase64), a pure
 | Function                       | Description                   |
 |--------------------------------|-------------------------------|
 | `quarto.base64.encode(str)`    | Encode a string into Base 64. |
-| `quarto.base64.decode(b64str)` | Decode a Base 64 string.      |
+| `quarto.base64.decode(b64str)` | Decode a Base 64 string.      |
+
+### Paths
+
+Quarto exposes paths to utilities that are likely to be useful to Lua extension and filter authors. Currently, only `quarto.paths.rscript()` is supported:
+
+| Function | Description |
+|---|---|
+| `quarto.paths.rscript()` | Returns the path to `Rscript` that Quarto uses in the `knitr` engine and R files for `quarto run` scripts |