Initial v2 release

What's new in v2

• Added support for multiple paths (#16), glob patterns, and single file caches (#33)
• Increased performance and improved cache sizes using zstd for compression for Linux and macOS runners (#184)
• Allowed caching for all events with a ref (#63)
• Created the @actions/cache npm package to allow other actions to utilize caching (#55)
• Added a best-effort step to delete the archive after extraction to reduces storage space (#209)