fix: filter out undefined values from query parameters in constructRequest leading to 400s

[par5ul1]

Noticed the /browse endpoint was broken when fetching playlist details via getPlaylistVideos, resulting in an Axios 400 Bad Request error. This fix filters out undefined query parameters in constructRequest to prevent invalid requests (e.g., continuation=undefined).

• Updated searchParams in constructRequest to exclude undefined values using Object.fromEntries and filter.
• Tested with playlist IDs to confirm the 400 error is resolved and videos load correctly.

Note: some tests are failing, but they were failing upon pull and first install. I thought it would being the scope of this PR to attempt and fix those too.

[par5ul1]

I think this also closes #51