Made `NSImage.symbol` optional (#20)

* Made NSImage.symbol optional

* Made NSImage.symbol optional

Fixed typos (#16)

Adding doc and split symbols (#15)

* Adjusted branch symbol to try to get it working with Ventura

* Adjusted branch symbol to try to get it working with Ventura

* Added doc and split symbols

Branch Symbol Compatibility (#14)

* Adjusted branch symbol to try to get it working with Ventura

* Adjusted branch symbol to try to get it working with Ventura

Added branch symbol (#13)

revert github symbol to SF Symbols v3

Merge pull request #11 from lukepistrol/feat/add-github-icon

add github symbol

Merge pull request #8 from zuziakaxel/fix/update-chevron-up-down