Add section about using snippets to contributing guide

Author: msimberg

docs/contributing/index.md

@@ -488,3 +488,12 @@ If you want to display commands without output that can easily be copied, use `b
     ```bash title="Hello, world!"
     echo "Hello, world!"
     ```
+
+### Avoiding repetition using snippets
+
+It can be useful to repeat information on different pages to increase visibility for users.
+If possible, prefer linking to a primary section describing a topic instead of fully repeating text on different pages.
+However, if you believe it's beneficial to actually repeat the content, consider using [snippets](https://facelessuser.github.io/pymdown-extensions/extensions/snippets/) to avoid repeated information getting out of sync on different pages.
+Snippets allow including the contents of a text file in multiple places of the documentation.
+
+For example, the recommended NCCL environment variables are defined in a text file (`docs/software/commuinication/nccl_env_vars`) and included on multiple pages because it's essential that users of NCCL notice and use the environment variables.