Update compile_esp8266.yml

Author: techniccontroller

.github/workflows/compile_esp8266.yml

@@ -23,7 +23,11 @@ jobs:
 
       - name: Configure Arduino CLI
         run: |
-          echo "board_manager:\n  additional_urls:\n    - 'http://arduino.esp8266.com/stable/package_esp8266com_index.json'" > .cli-config.yml
+          cat <<EOF > .cli-config.yml
+          board_manager:
+            additional_urls:
+              - http://arduino.esp8266.com/stable/package_esp8266com_index.json
+          EOF
           arduino-cli config init --config-file .cli-config.yml
           arduino-cli core update-index --config-file .cli-config.yml
           arduino-cli core install esp8266:esp8266 --config-file .cli-config.yml