Add instructions for debugging dawn.node with gdb/lldb

Bug: dawn:1123
Change-Id: I25dd0b724903a6dcce276bd7744fd12a21a9137e
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/85360
Reviewed-by: Ben Clayton <bclayton@google.com>
Commit-Queue: Corentin Wallez <cwallez@chromium.org>

src/dawn/node/README.md

@@ -118,6 +118,21 @@ Replacing:
 - `[path-to-dawn.node]` this the path to the `dawn.node` module built by the [build step](#Build)
 - `test-query` with the test query string. Example: `webgpu:shader,execution,builtin,abs:*`
 
+## Debugging dawn-node issues in gdb/lldb
+
+It is possible to run the CTS with dawn-node directly similarly to Debugging TypeScript with VSCode:
+
+```sh
+cd <cts-root-dir>
+[path-to-node] \ # for example <dawn-root-dir>/third_party/node/<arch>/node
+    -e "require('./src/common/tools/setup-ts-in-node.js');require('./src/common/runtime/cmdline.ts');" \
+    -- \
+    dummy-arg \
+    --gpu-provider [path to dawn.node] \
+    [test-query]
+```
+
+This command is then possible to run in your debugger of choice.
 
 ## Known issues