Topology documentation

The current topology interface stabilizes slowly and I think I would like to keep it experimental for the release. However, we should start documenting it and ExclusiveTopology in examples. As suggested by @koehlerson in https://github.com/Ferrite-FEM/Ferrite.jl/pull/758#issuecomment-1761159628 we might want to include svg plots or ascii art about the queries and theory. IMO there should be
1. one section in the topic guide containing definitions and reasoning on `ExclusiveTopology` (and maybe `CoverTopolgy` if we want to move it from FerriteDistributed.jl to Ferrite.jl).
2. Some how-to's using the topology, e.g. to compute Laplace stencils, also to see how the design works out.