Isotopic "exact masses"

[ghutchis]

Right now, the properties only list molecular mass. Many times (e.g., mass spec) one wants the isotopic exact mass instead.

We should implement the exact mass for the most abundant isotopes (and perhaps also the full table of isotopic masses).

e.g. https://www.nist.gov/pml/atomic-weights-and-isotopic-compositions-relative-atomic-masses

[harshit4311]

I would like to work on this!