Update specifying-dependencies-and-devdependencies-in-a-package-json-… (#1221)

…file.mdx

mention shortcut flags

<!-- What / Why -->
for convenience, mention abbreviated versions of `--save-prod` and
`--save-dev`

Author: shallow-beach

content/packages-and-modules/contributing-packages-to-the-registry/specifying-dependencies-and-devdependencies-in-a-package-json-file.mdx

@@ -13,7 +13,7 @@ You can add dependencies to a `package.json` file from the command line or by ma
 
 ### Adding dependencies to a `package.json` file from the command line
 
-To add dependencies and devDependencies to a `package.json` file from the command line, you can install them in the root directory of your package using the `--save-prod` flag for dependencies (the default behavior of `npm install`) or the `--save-dev` flag for devDependencies.
+To add dependencies and devDependencies to a `package.json` file from the command line, you can install them in the root directory of your package using the `--save-prod` flag (also `-S`) for dependencies (the default behavior of `npm install`) or the `--save-dev` flag (also `-D`) for devDependencies.
 
 To add an entry to the `"dependencies"` attribute of a `package.json` file, on the command line, run the following command: