Add CI pipeline running the codespell tool

.gitlab-ci.yml

CHANGELOG.md

cmake/modules/FindARPACK.cmake

cmake/modules/FindARPACKPP.cmake

doc/istl.tex

dune/istl/basearray.hh

dune/istl/bcrsmatrix.hh

dune/istl/ildl.hh

dune/istl/io.hh

dune/istl/multitypeblockvector.hh

dune/istl/novlpschwarz.hh

dune/istl/overlappingschwarz.hh

dune/istl/owneroverlapcopy.hh

dune/istl/paamg/aggregates.hh

dune/istl/paamg/test/anisotropic.hh

dune/istl/paamg/test/fastamg.cc

dune/istl/preconditioner.hh

dune/istl/preconditioners.hh

dune/istl/repartition.hh

dune/istl/scalarproducts.hh