add pressure units MilligramForcePerSquareFoot and MilligramForcePerS…

[TS-Andritz]

Adding two units used in our domain for small pressure values in two different systems of measurement (metric and US customary).

[angularsen]

Hi and thanks for contributing, although these units are probably a bit niche it seems useful enough to include.

Use exact coefficients for MilligramForcePerSquareFoot

Per our conversion function guidelines, prefer exact constituent constants over pre-computed decimals so the physical constants remain visible and no precision is lost.

The MilligramForcePerSquareFoot conversion uses a pre-computed decimal.

Please change from:

"FromUnitToBaseFunc": "{x} * 1.0555790208802639466e-4",
"FromBaseToUnitFunc": "{x} / 1.0555790208802639466e-4",

To:

"FromUnitToBaseFunc": "{x} * 9.80665e-6 / 9.290304e-2",
"FromBaseToUnitFunc": "{x} / 9.80665e-6 * 9.290304e-2",

This keeps the exact definition constants visible (9.80665 = standard gravity, 9.290304e-2 = ft² in m²) and avoids precision loss from pre-computation.

Otherwise LGTM

Naming, localization, and test values all look correct.

[TS-Andritz]

Hi, thanks for your reply.

I just made the change and pushed the commit.

Regarding the units, we were ourself a bit surprised by this combination of metric and imperial units, but it seems to be used by metalworking companies, specifically in the "US Customary" system of measurements.