S3 class constants

`constants(.x, use_tealeaves)`

- .x
A list to be constructed into

**constants**.- use_tealeaves
Logical. Should leaf energy balance be used to calculate leaf temperature (T_leaf)? If TRUE,

`tleaf()`

calculates T_leaf. If FALSE, user-defined T_leaf is used. Additional parameters and constants are required, see`make_parameters()`

.

Constructor function for constants class. This function ensures that physical constant inputs are properly formatted.