Extend req.io to Windows and Linux platform

[Nithin18]

As a user, I want to download and use req.io on Windows and Linux operating systems, without needing to have a macOS device, so that I can test APIs on my preferred platform.

Acceptance Criteria

• Given I am a Windows user visiting the releases page When I download the Windows installer Then I should be able to install and launch req.io successfully.

• Given I am a Linux user visiting the releases page When I download the Linux package (AppImage or .deb) Then I should be able to run or install req.io and launch it successfully

• Given I am using req.io on Windows When I send HTTP requests, modify headers, add query params, and configure authentication Then all features should work exactly as they do on macOS

• Given I am using req.io on Linux When I send HTTP requests, modify headers, add query params, and configure authentication Then all features should work exactly as they do on macOS

• Given I visit the releases page When I look for downloads Then I should see separate installers available for Windows, Linux, and macOS

• Given I visit the README When I want to install req.io Then I should find clear installation instructions for my operating system (Windows, Linux, or macOS)

Note: Build configurations for all platforms already exist in electron-builder.json5 and package.json. The main work is updating the CI/CD workflow from macOS-only to multi-platform builds and performing cross-platform testing.

[kannananil]

Hi @Nithin18, thanks for adding this. Lets prioritise this for the upcoming milestone v0.2.0