Release v0.21.1

[johanjanssens]

1. Discover extension name from extension manifest #733

Made it possible to specify the extension name in the manifest. The extension name is the name the extension is registered with in the autoloader.

By specifying the name you can now use a different extension directory or phar name for your extensions. Making it possible to including additional info in the phar name or extension directory, like the version etc.

Fixes

• Fixed breaking changes in example blog site [site:blog] - Fix issues #734
• Update prefetcher url Update prefetcher url #730