Markers (start, mid, end) (arrow heads, etc)

[techniq]

• https://developer.mozilla.org/en-US/docs/Web/SVG/Element/marker
• https://svgwg.org/specs/markers/
• http://tutorials.jenkov.com/svg/marker-element.html
• https://observablehq.com/@basilesimon/arrowheads-on-axes
• https://github.com/airbnb/visx/tree/master/packages/visx-marker
  • https://airbnb.io/visx/curves
• https://observablehq.com/@bumbeishvili/svg-markers
• https://observablehq.com/@observablehq/plot-custom-markers
• Globe with geomark icons