Add section to contributing guide

CONTRIBUTING.md

@@ -4,6 +4,11 @@ Wrangler is an open source project and we welcome contributions from you. Thank
 
 Below you can find some guidance on how to be most effective when contributing to the project.
 
+## Before getting started
+We really appreciate your interest in making a contribution, and we want to make sure that the process is as smooth and transparent as possible! To this end, we note that the Workers team is actively doing development in this repository, and while we consistently strive to commnicate status and current thinking around all open issues, there may be times when context surrounding certain items is not up to date. Therefore, **for non-trivial changes, please always engage on the issue or create a discussion or feature request issue first before writing your code.** This will give us opportunity to flag any considerations you should be aware of before you spend time developing. Of course for trivial changes, please feel free to go directly to filing a PR, with the understanding that the PR itself will serve as the place to discuss details of the change.
+
+Thanks so much for helping us improve the [workers-sdk](https://github.com/cloudflare/workers-sdk), and we look forward to your contribution!
+
 ## Getting started
 
 ### Set up your environment