docs: add sop for adding new routes to the worker

docs/sops/adding-new-routes.md

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+# Adding New Routes
+
+Guide on how to add new routes for the Release Worker to handle.
+
+This assumes:
+
+- There has already been prior discussions regarding the new routes
+- A concensus has been reached on what routes are needed and how they are to function.
+
+If there hasn't been a discussion, please [open a issue](https://github.com/nodejs/release-cloudflare-worker/issues/new) on this repository to discuss it.
+
+## Steps
+
+- Write the code/symlinks/... that handles the route and open a PR on this repository.
+  - Please be intentional for any middleware that the new route is using. Verify that the middleware can handle that route.
+  - Example: [#331](https://github.com/nodejs/release-cloudflare-worker/pull/331)
+- Open an issue on [nodejs/build](https://github.com/nodejs/build) requesting the new route be sent to the Release Worker
+  - This can be done before or after the PR for the Release Worker is merged.
+  - Example: [nodejs/build#4044](https://github.com/nodejs/build/issues/4044).
+
+> [!IMPORTANT]
+> If the route is for new files included in a release, a release must be made with those files present before the PR here gets merged.