Link to node-glob's "glob primer"

As mentioned in #1707.

README.md

@@ -158,8 +158,10 @@ In practice, this may look something like:
 prettier --single-quote --trailing-comma es5 --write "{app,__{tests,mocks}__}/**/*.js"
 ```
 
-(Don't forget the quotes around the globs! The quotes make sure that Prettier
-expands the globs rather than your shell, for cross-platform usage.)
+Don't forget the quotes around the globs! The quotes make sure that Prettier
+expands the globs rather than your shell, for cross-platform usage.
+The [glob syntax from the glob module](https://github.com/isaacs/node-glob/blob/master/README.md#glob-primer)
+is used.
 
 Prettier CLI will ignore files located in `node_modules` directory. To opt-out from this behavior use `--with-node-modules` flag.