new cloud microphysics example using Unitful.jl

[thearia0]

Checklist

• [ x] Appropriate tests were added
• [x ] Any code changes were done in a way that does not break public API
• x[ ] All documentation related to code changes were updated
• [x ] The new code follows the contributor guidelines, in particular the SciML Style Guide and COLPRAC.
• [ x] Any new documentation only uses public API

Additional context

I propose a new example to be included in the "Beginniners" section. The example includes a solution of a classic problem in cloud microphysics and succesfully reproduces all figures from the Rogers 1975 paper (open access) referenced from the .md file. The example also shows a robust way to couple DiffEq.jl with Unitfull.jl to enable dimensional analysis of the code for testing, while not incurring any overhead during integration (https://discourse.julialang.org/t/unitful-jl-and-differentialequations-jl-compatibility/68594).

(BTW, this PR constitutes a basis of an engineering project carried out at the Faculty of Physics and Applied Computer Science, AGH University of Krakow - to be defended in January 2026)