This PR implements a flexible operator registry system that allows users to create custom operator sets for different use cases. The new system provides:

New Classes

OperatorRegistry

A class to manage collections of operators with methods to:

• Add/remove operators dynamically
• Check operator existence (including aliases)
• Clone and merge registries
• Convert to efficient lookup maps

ExpressionRuntime

A runtime class that evaluates JSON expressions using a specified operator registry:

const runtime = new ExpressionRuntime(customRegistry);
const result = runtime.evaluate(['+', 1, 2], {vars: new Vars(null)});

ExpressionCodegen

A code generation class that compiles expressions to JavaScript using custom operator sets:

const codegen = new ExpressionCodegen(registry, {expression: ['+', 1, 2]});
const compiledFn = codegen.run().compile();

Built-in Registries

Default Registry

Contains the most commonly used operators for typical JSON expression needs:

• Arithmetic (+, -, *, /, etc.)
• Comparison (==, >, <, etc.)
• Logical (and, or, not)
• Type checking (type, bool?, str?, etc.)
• Container operations (len, member)
• String operations (cat, contains, starts)
• Array operations (concat, filter, map)
• Object operations (keys, values, entries)
• Control flow (if, throw)
• Variable access (get, $)

Extended Registry

Includes everything from the default registry plus advanced operators:

• Binary operations (u8, i8, f32, etc.)
• Bitwise operations (&, |, ^, ~)
• JSON Patch operations (jp.add)

Usage Examples

import { 
  defaultOperatorRegistry, 
  extendedOperatorRegistry,
  OperatorRegistry,
  ExpressionRuntime 
} from '@jsonjoy.com/json-expression';

// Use default operators for common cases
const runtime = new ExpressionRuntime(defaultOperatorRegistry);
const result = runtime.evaluate(['+', 1, 2], {vars: new Vars(null)}); // 3

// Use extended registry for advanced operations  
const extendedRuntime = new ExpressionRuntime(extendedOperatorRegistry);
const bitwiseResult = extendedRuntime.evaluate(['&', 5, 3], {vars: new Vars(null)}); // 1

// Create custom registries
const customRegistry = new OperatorRegistry()
  .add(...arithmeticOperators)
  .add(...comparisonOperators);

Backward Compatibility

All existing APIs remain unchanged. The original evaluate function and JsonExpressionCodegen class continue to work exactly as before, using the full operator set by default.

Fixes #3.

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