fix: resolve property name conflicts in StructRow.toJSON()[#95]

[Divyanshu-s13]

What's Changed

Fixed a bug in StructRow.toJSON() where field names that match built-in JavaScript object properties (like size, length, toString, etc.) would incorrectly return the built-in property value instead of the actual column data.

The Problem

When a struct had a column named size and you called row.toJSON(), it would return the built-in size property of the object instead of the value from the size column.

The Solution

Modified the toJSON() method in src/row/struct.ts to store the field name in a local variable before using it to access the JSON object. This prevents property name conflicts with built-in object properties.

Closes #95

[kou]

Could you add a test for this?

[Divyanshu-s13]

@kou I fixed this issue. Could you please merge it?

[Divyanshu-s13]

@kou By the way, I’m planning to apply for GSoC this year and really enjoying contributing here.
I’d love to align my work with areas that matter most to the project.

[kou]

Could you add a test for this?