<bmx-formula-engine>
A spreadsheet calculation engine as an element.
No script runs this calculator. The engine holds the sheet; inputs with
data-bmx-cell edit cells, and anything else with it shows the cell's value in its format.
Type 5% or £300,000 - text is read as a person means it.
Every property, event and method: https://docs.binarymission.co.uk/webcomponents/bmx/bmx-formula-engine.html