Briefly introduce debugging and debuggers

[SimonClifford]

In the Learn section (say somewhere around https://fortran-lang.org/learn/building_programs/) would it be useful to have a brief introduction to debugging? We mention compilation, linking, run time libraries, build tools, and distribution. "Options for debugging" is mentioned at the end of (https://fortran-lang.org/learn/building_programs/compiling_source/) but nothing to say how this will help the user!

I'm happy to look at this if the community feels it's needed.