feat: support for appending to array at path

[rmehri01]

• add /[] syntax to path that will append instead of overwriting the value at the path

For example, if we have a pyproject.toml with the following contents:

[tool.uv.sources]
torch = [{ index = "foo", marker = "platform_system == 'Windows'" }]

Then applying:

jq -c -n '[{op: "add", table_header_path: "tool/uv/sources", path: "torch/[]", value: "{\"index\": \"pytorch-cpu\"}"}]' | cargo run -- --path pyproject.toml

Will result in the following contents in pyproject.toml:

[tool.uv.sources]
torch = [{ index = "foo", marker = "platform_system == 'Windows'" }, { index = "pytorch-cpu" }]

• also fix some clippy lints

[blast-hardcheese]

Fantastic. Thanks for the back and forth, I think this DX is solid, and will continue to offer opportunities for further extensibility (path: foo/bar/[]/baz/blix as an example).

Thank you!