Expand readme with usage examples and streaming JSONL section

[Copilot]

Adds practical usage examples and documents the async streaming API for JSONL processing.

New examples under Usage

• Reshaping objects — object construction to project/flatten nested fields
• Optional fields and defaults — // alternative operator for absent/null fields
• Array operations — group_by + map for collection aggregation

New Streaming JSONL section

Documents Jq.EvaluateAsync with IAsyncEnumerable<JsonElement> input:

using var stream = File.OpenRead("users.jsonl");
var elements = JsonSerializer.DeserializeAsyncEnumerable<JsonElement>(
    stream, topLevelValues: true);

await foreach (var result in Jq.EvaluateAsync("select(.dept == \"Engineering\") | .name", elements))
    Console.WriteLine(result);

Covers three patterns: one-shot stream filtering, reusing a pre-parsed JqExpression across multiple streams, and CancellationToken integration.

Note: JQSharp does not support the shorthand {field} object constructor syntax — all examples use explicit {key: expr} form.

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💡 You can make Copilot smarter by setting up custom instructions, customizing its development environment and configuring Model Context Protocol (MCP) servers. Learn more Copilot coding agent tips in the docs.

[kzu]

🧪 Details on Ubuntu 24.04.3 LTS

from retest v1.1.0 on .NET 10.0.3 with 💜 by @devlooped