Add UOM benchmark.

[iliekturtles]

Makes use of the just published uom v0.13.0. Still a few warts (none should affect benchmark numbers once resolved):

• G requires transmute to setup. Ugly but will be resolved by Create constructor method for unnamed quantities iliekturtles/uom#28.
• dist calculation requires calling get, sqrt, and new instead of just calling sqrt on the Area. Will be resolved by Implement float methods iliekturtles/uom#11.
• Constants can't actually be defined as const. Quantity's fields are an implementation detail and private and struct constructors (not constructor methods) are the only way to initialize constants right now. const fn isn't stable yet.

[coder543]

Done! thanks for contributing this!