align SFSymbols left and right to the guides

[swhitty]

Updates the alignment of SFSymbols and left/right guides to precisely align to the supplied insets.

When --insets auto is used the left/right guides are placed 10pt from the detected paths which is similar to how many official symbols are aligned;

When a single --insets are supplied, these insets are now automatically used for all variants;

% swiftdraw image.svg --format sfsymbol --insets 10 20 10 20
Alignment: --insets 10 20 10 20
Alignment: --ultralightInsets 10 20 10 20
Alignment: --blackInsets 10 20 10 20