Changes from v2.6.0:
This release changes a lot of methods, please see the upgrade guide.

• replace sync getters and generate() with async methods (see async / stream support #195).
• support nodejs streams (in file() and generateAsync()).
• support Blob and Promise in file() and loadAsync() (see [JSZip v3] Blob, Promise and more. #275).
• add support.nodestream.
• zip.filter: remove the defensive copy.
• remove the deprecated API (see Implement breaking changes for JSZip v3. #253).
• type is now mandatory in generateAsync().
• change the createFolders default value (now true).
• Dates: use UTC instead of the local timezone.
• Add base64 and array as possible output type.
• Add a forEach method.
• Drop node 0.8 support (see [breaking change] JSZip v3: drop node 0.8 support. #270).