add intruction on rendering single qmd (#469)

Author: yebai

README.md

@@ -3,7 +3,9 @@
 This repository contains the Turing.jl documentation and tutorials. 
 
 - The `master` branch contains the quarto source 
-- The `gh-pages` branch contains the `html` version of these documents compiled from the `master` branch. 
+- The `gh-pages` branch contains the `html` version of these documents compiled from the `master` branch.
+
+This repository is part of [Turing.jl's](https://turinglang.org/) Website, i.e. `https://turinglang.org/docs/`. You can see the main website's repo [here](https://github.com/TuringLang/turinglang.github.io).
 
 To get started with the docs website locally, you'll need to have the following prerequisite installed:
 
@@ -38,7 +40,12 @@ Note: Avoid clicking links in the navbar while previewing locally because they w
     ```
 This will render the full website in `_site` folder.
 
-This repository is part of [Turing.jl's](https://turinglang.org/) Website, i.e. `https://turinglang.org/docs/`. You can see the main website's repo [here](https://github.com/TuringLang/turinglang.github.io).
+It is also possible to render a single tutorial or `qmd` file without compiling the entire site. This is often helpful to speed up compilation when editing on a single docs page. To do this, first `cd` to the file's folder, and run `quarto preview` or `quarto render`: 
+
+```
+cd folder_of_somedocs.qmd
+quarto render somedocs.qmd
+```
 
 ## License