Extract environment-agnostic logic into @hawk.so/core

[FeironoX5]

Currently, @hawk.so/javascript contains both environment-agnostic logic and browser-specific implementation details. We should restructure the package architecture by separating shared core logic from runtime-specific code.

Proposed plan

1. Move shared logic from @hawk.so/javascript into @hawk.so/core
2. Move browser-specific logic from @hawk.so/javascript into @hawk.so/browser

Considerations

• We should later move @hawk.so/nodejs & @hawk.so/nuxt into this repository to reuse functionality from @hawk.so/core
• We should discuss how to make migration without any changes to the public API or dependency names