Update vendor function from vendor_pkgs to vendor_crates (#90)

Author: ryanzomorrodi

user-guide/cran-publishing.qmd

@@ -5,7 +5,7 @@ title: Publishing to CRAN
 extendr-based packges are CRAN compatible **out of the box**! You only have to do _one_ additional step—vendor your Rust dependencies. 
 
 ```r
-rextendr::vendor_pkgs()
+rextendr::vendor_crates()
 ```
 
 That's it!
@@ -32,6 +32,6 @@ CRAN does not support nightly features as of this writing. Any package you plan
 
 One of the reasons we love CRAN is that they take portability seriously. Because of this, an R package must contain everything it needs to build. This means that the Rust dependencies must not be downloaded as the package is installed. 
 
-Vendoring is the process of embedding the source code of our dependencies into our R package. `vendor_pkgs()` creates a `vendor.tar.xz` file which contains the compressed source of all the dependencies. 
+Vendoring is the process of embedding the source code of our dependencies into our R package. `vendor_crates()` creates a `vendor.tar.xz` file which contains the compressed source of all the dependencies.