Fix reference to list of constants in the README (#52)

Created a link to the full list of physical constants in the documentation since it doesn't seem to be part of the README anymore.

[skip ci]

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Co-authored-by: Mosè Giordano <765740+giordano@users.noreply.github.com>

Author: nathanrboyer

README.md

@@ -60,7 +60,7 @@ Reference                     = CODATA 2022
 
 `SpeedOfLightInVacuum` and `NewtonianConstantOfGravitation` are two of the
 `PhysicalConstant`s defined in the `PhysicalConstants.CODATA2022` module, the
-full list of available constants is given below.
+[full list of available constants](https://juliaphysics.github.io/PhysicalConstants.jl/stable/constants/) is given in the documentation.
 
 `PhysicalConstant`s can be readily used in mathematical operations, using by
 default their `Float64` value: