Update actions/checkout action to v7

.github/workflows/esp32_build.yml

@@ -21,7 +21,7 @@ jobs:
 
     steps:
       - name: Checkout repo
-        uses: actions/checkout@v4
+        uses: actions/checkout@v7
         with:
           submodules: "recursive"
       - name: ESP-IDF build

renovate.json

@@ -0,0 +1,3 @@
+{
+  "$schema": "https://docs.renovatebot.com/renovate-schema.json"
+}