Introduce PhysicalConstants and new energy units

[ytdHuang]

Checklist

Thank you for contributing to QuantumToolbox.jl! Please make sure you have finished the following tasks before opening the PR.

• Please read Contributor Covenant Code of Conduct
• Any code changes were done in a way that does not break public API
• Appropriate tests were added and tested locally by running: make test.
• Any code changes should be julia formatted by running: make format.
• All documents (in docs/ folder) related to code changes were updated and able to build locally by running make docs.

Request for a review after you have completed all the tasks. If you have not finished them all, you can also open a Draft Pull Request to let the others know this on-going work.

Description

Summary of this PR:

• Introduce const PhysicalConstants::NamedTuple, which stores some constant values listed in CODATA recommended values of the fundamental physical constants: 2022
• Add new energy units for convert_unit

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 93.51%. Comparing base (c7a3483) to head (3269f6d).
Report is 2 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #257      +/-   ##
==========================================
- Coverage   94.38%   93.51%   -0.88%     
==========================================
  Files          31       31              
  Lines        2297     2297              
==========================================
- Hits         2168     2148      -20     
- Misses        129      149      +20     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

[albertomercurio]

I don't know if we want to use the PhysicalConstants.jl package at this point.

[ytdHuang]

I don't know if we want to use the PhysicalConstants.jl package at this point.

But they didn't update the values for a while.
So I think maybe we just make it by ourselves.