add readme

Author: critesjosh

custom-note/README.md

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+# Custom Note Contract
+
+An Aztec Noir contract demonstrating how to create and use custom note types in the Aztec protocol.
+
+## Overview
+
+This project showcases how to define a custom note structure with multiple fields and use it in a private smart contract. The contract stores custom notes in a private state that can only be viewed by the note owner.
+
+## Custom Note Structure
+
+The `CustomNote` contains:
+
+- **a, b, c, d**: Four arbitrary `Field` values for custom data
+- **randomness**: A random `Field` value to ensure note privacy
+- **owner**: The `AztecAddress` of the note owner
+
+## Contract Functions
+
+### `insert(a: Field, b: Field, c: Field, d: Field)`
+
+A private function that creates and stores a new custom note.
+
+- **Parameters**: Four field values (a, b, c, d)
+- **Behavior**: Creates a note with the provided values and assigns ownership to the message sender
+- **Privacy**: Emits the note using unconstrained onchain message delivery
+
+### `view_custom_notes(owner: AztecAddress)`
+
+An unconstrained utility function to view all custom notes for a given owner.
+
+- **Parameters**: Owner's Aztec address
+- **Returns**: Array of custom notes (up to `MAX_NOTES_PER_PAGE`)
+- **Usage**: Can be called to query notes without consuming gas
+
+## Building
+
+Compile the contract using Nargo:
+
+```bash
+nargo compile
+```
+
+## Usage Example
+
+1. **Deploy the contract** to an Aztec network
+
+2. **Insert a custom note**:
+
+   ```noir
+   CustomNote.insert(field1, field2, field3, field4)
+   ```
+
+3. **View notes for an address**:
+   ```noir
+   CustomNote.view_custom_notes(owner_address)
+   ```
+
+## Key Features
+
+- Demonstrates custom note type implementation with the `#[note]` macro
+- Shows how to use `PrivateSet` storage for managing multiple notes per user
+- Implements proper note privacy using randomness
+- Provides getter methods for accessing individual note fields
+
+## Dependencies
+
+- Aztec Noir v3.0.0-nightly.20251107
+- Nargo >= 1.0.0
+
+## Project Structure
+
+```
+custom-note/
+├── Nargo.toml           # Project configuration
+└── src/
+    ├── main.nr          # Main contract implementation
+    └── custom_note.nr   # Custom note type definition
+```
+
+## Learn More
+
+- [Aztec Documentation](https://docs.aztec.network/)
+- [Noir Language Documentation](https://noir-lang.org/)