Add the 1D wave.jl documentation into example.md

[cquiroz1031]

Adds a new subsection to examples.md containing documentation for the wave.jl 1D wave equation example implemented with ClimaCore.
This documentation is intended to provide a simple, self-contained example for new users of ClimaCore.

• Code follows the style guidelines OR N/A.
• Unit tests are included OR N/A.
• Code is exercised in an integration test OR N/A.
• Documentation has been added/updated OR N/A.

[valeriabarra]

Hi @cquiroz1031 , thank you for your contribution!

There are a couple of error messages in the doc build. It is recommended that you test the doc build on your local machine before pushing to the PR.

┌ Error: invalid local link/image: path pointing to a file outside of build directory in docs/src/examples.md
│   link =
│    @ast MarkdownAST.Image("../assets/wave_end.png", "") do
│      MarkdownAST.Text("wave_end.png")
│    end
│    
└ @ Documenter ~/.julia/packages/Documenter/tbj1p/src/utilities/utilities.jl:47
┌ Error: invalid local link/image: path pointing to a file outside of build directory in docs/src/examples.md
│   link =
│    @ast MarkdownAST.Image("../assets/wave.gif", "") do
│      MarkdownAST.Text("wave.gif")
│    end
│    
└ @ Documenter ~/.julia/packages/Documenter/tbj1p/src/utilities/utilities.jl:47

To see these error messages, click on the failing GitHub Action check:

Try to fix these locally and push to your branch again. Thank you