docs: converter readme (#8)

Author: fmorency

contracts/converter/README.md

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+# Converter Contract
+
+A CosmWasm smart contract for converting between MFX and different token denominations on the Manifest Network. This contract enables secure token conversion using configurable exchange rates and authorization mechanisms.
+
+## Overview
+
+The Converter contract facilitates the conversion of MFX tokens to target tokens at a predetermined exchange rate. 
+
+## Features
+
+- **Token Conversion**: Convert between any two token denominations
+- **Configurable Exchange Rate**: Set custom conversion rates using decimal precision
+- **Pause Functionality**: Emergency pause mechanism to halt conversions
+- **Admin Controls**: Administrative functions for configuration management
+
+## Contract Architecture
+
+### Key Components
+
+- **Rate System**: Handles exchange rate calculations and validation
+- **Denomination Management**: Validates and manages source/target token types
+- **Admin Controls**: Manages contract administration and configuration updates
+- **Conversion Logic**: Orchestrates the burn-and-mint token conversion process
+
+### State Management
+
+The contract maintains:
+- **Config**: Core configuration including rates, denominations, and pause state
+- **Admin**: Contract administrator with privileged access
+
+## Messages
+
+### Instantiate
+
+Initialize the contract with configuration parameters:
+
+```json
+{
+  "admin": "manifest1...",
+  "poa_admin": "manifest1...",
+  "rate": "1.5",
+  "source_denom": "utoken1",
+  "target_denom": "utoken2",
+  "paused": false
+}
+```
+
+### Execute Messages
+
+#### Convert
+Convert source tokens to target tokens:
+```json
+{
+  "convert": {}
+}
+```
+*Note: Send the source tokens as funds with this message*
+
+#### Update Config
+Update contract configuration (admin only):
+```json
+{
+  "update_config": {
+    "config": {
+      "poa_admin": "manifest1...",
+      "rate": "2.0",
+      "source_denom": "unewtoken",
+      "target_denom": "uanothertoken",
+      "paused": true
+    }
+  }
+}
+```
+
+#### Update Admin
+Transfer admin privileges (admin only):
+```json
+{
+  "update_admin": {
+    "admin": "manifest1..."
+  }
+}
+```
+
+### Query Messages
+
+#### Config
+Get current contract configuration:
+```json
+{
+  "config": {}
+}
+```
+
+#### Admin
+Get current admin address:
+```json
+{
+  "admin": {}
+}
+```
+
+## Development
+
+### Building
+```bash
+cargo wasm
+```
+
+### Testing
+```bash
+cargo test
+```
+
+## Migration
+
+The contract supports migration with version checking to ensure compatibility. Migration logic can be extended as needed for future versions.
+
+## License
+
+Apache-2.0
+
+## Links
+
+- **Repository**: https://github.com/manifest-network/manifest-contracts
+- **Homepage**: https://manifest.network