add tldr to contributing (#10417)

Author: emily-shen

CONTRIBUTING.md

@@ -4,6 +4,20 @@ 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.
 
+## tl;dr for contributing to Wrangler
+
+Useful commands for developing Wrangler (all commands below should be run in the project root):
+
+- `pnpm i; pnpm build` will build everything in workers-sdk.
+- `pnpm dev -F wrangler` will watch and build changes while you develop. Fixtures use the build output from this, and are useful for messing around during dev (`fixtures/worker-ts` is a useful blank slate).
+
+Before committing/submitting a PR:
+
+- Add [tests](#pr-tests). `pnpm test -F wrangler` will run Wrangler's unit tests. You can filter tests: e.g. `pnpm test -F wrangler "containers"`.
+- Run `pnpm check` for typechecking and linting.
+- Add a [changeset](#changesets) with `pnpm changeset`.
+- Don’t squash your commits after a review.
+
 ## 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 communicate 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.