feat: new library Hexagonal Sticky Notes ("Hexies")

[excalibot]

Hexagonal-shaped sticky notes in light and dark variants.

Useful for small group brainstorming or planning sessions (e.g. Future Backward exercise - https://wiki.cynefin.net/index.php/Future_backwards).

Submitted by @quinn-p-mchugh

Items: Hexagonal Sticky Note - Dark Red, Hexagonal Sticky Note - Dark Orange, Hexagonal Sticky Note - Dark Yellow, Hexagonal Sticky Note - Dark Teal, Hexagonal Sticky Note - Dark Green, Hexagonal Sticky Note - Dark Maroon, Hexagonal Sticky Note - Dark Pink, Hexagonal Sticky Note - Dark Purple, Hexagonal Sticky Note - Dark Blue, Hexagonal Sticky Note - Dark Cyan, Hexagonal Sticky Note - Dark Brown, Hexagonal Sticky Note - Dark Gray, Hexagonal Sticky Note - Light Red, Hexagonal Sticky Note - Light Orange, Hexagonal Sticky Note - Light Yellow, Hexagonal Sticky Note - Light Teal, Hexagonal Sticky Note - Light Green, Hexagonal Sticky Note - Light Maroon, Hexagonal Sticky Note - Light Pink, Hexagonal Sticky Note - Light Purple, Hexagonal Sticky Note - Light Blue, Hexagonal Sticky Note - Light Cyan, Hexagonal Sticky Note - Light Brown, Hexagonal Sticky Note - Light Gray, Hexagonal Sticky Note - White, Hexagonal Sticky Note - Black

Installation link