docs: readme

README.md

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+# Raspberry PI Pico W Doorbell
+
+This is a simple doorbell built on the Raspberry Pi Pico W with Zig and the Pico C SDK.
+
+# Usage
+
+Create a setting.json in the src folder similar to this one:
+```json
+{
+    "ssid": "YOUR_WIFI_NAME",
+    "password": "WIFI_PASSWORD",
+    "ntfy_url":"http://ntfy.sh/YOUR_CHANNEL_NAME"
+}
+```
+
+***Note: Without this file, the project will not compile!***
+
+The content of the settings.json is processed comptime so the file will not be placed on the pico.