Image uploading using XHR

1. Cloudinary as file storage
2. Nextjs api-routes to get signed URLs from Cloudinary for uploading images
3. react-spring for showing upload progress

to use: add this env variables:

CLOUDINARY_API_SECRET=your_cloudinary_api_secret
NEXT_PUBLIC_CLOUDINARY_API_KEY=your_cloudinary_api_key
NEXT_PUBLIC_CLOUDINARY_CLOUD_NAME=your_cloudinary_cloud_name
NEXT_PUBLIC_CLOUDINARY_UPLOAD_URL=your_cloudinary_upload_url