Tips:

- "Loose" propagations can be done by making dummy variables in the form of cell references (A1, A2, etc.)
- Sheet specified references will be treated separate from implicit.
- This system is only good at "math" functions (e.g. tan(), ln(), sqrt()) right now. (no xlookup() or average())

- Using my fork of Deriv.
- Huge thanks to Hugh O'Reilly's original repo!
- MathJax to render LaTeX.

- Add overall err prop equation sqrt(sum()) with step-by-step evaluation from the placeholder variables
- Add hover events to td elements for clipboard interactions
- Figure out LaTeX to image to clipboard pathway
- Add loading popups to give feedback
- Combine all variable settings into one table at top of output
- Incorporate error cell setting for each variable.
- Fix decimal passing in deriv.
- Allow mixing of "$A$5" with "$A5" or "A5" (separate group for sheet-specified).
- Allow mixing of "$A$5" with "Sheet4!$A$5" (add check for match neighbors).
- Add understanding of propagation for basic functions like AVERAGE(), STDEV(), and LINEST().