Fix CI failure due to checking out non-existent branch

.github/workflows/build.yml

@@ -1,6 +1,7 @@
 name: Build
-on: 
+on:
   push:
+  pull_request:
   workflow_dispatch:
     inputs:
       memory:
@@ -17,7 +18,6 @@ jobs:
     - name: Checkout pixie-firmware
       uses: actions/checkout@v3
       with:
-        ref: chore/add-submodules
         submodules: 'recursive'
     - name: Setup node version
       uses: actions/setup-node@v4

README.md

@@ -33,6 +33,21 @@ Use [docker](https://docs.docker.com/engine/install) to build the project:
 docker run --rm -v $PWD:/project -w /project -e HOME=/tmp espressif/idf idf.py build
 ```
 
+Troubleshooting
+---------------
+
+1. If you get `error: implicit declaration of function x; did you mean function y? [-Wimplicit-function-declaration]`, check and update the `firefly-scene` and `firefly-display` submodules in the components folder:
+
+```sh
+# check the submodules are from the correct branch
+git submodule status
+
+# update the submodules
+git submodule update --init --recursive
+
+# pull submodules changes from the remote repositories
+git pull --recurse-submodules
+```
 
 
 Hardware Specifications