Add whats new link for 3.8 #5564

Job	Run time
black	29s
clang-format	20s
copyright_headers	22s
cppcheck	8m 15s
flake8	25s
forbidden_types	14s
isort	12s
lychee_IGNORED	22s
mypy	34s
pydocstyle	24s
pylint	38s
rstcheck	25s
unused_names	14s
vale	33s
sphinx-rtd	3m 27s
sphinx-conda	0s
build_macos (macos-latest, clang, openmp, mpi, python, gsl, ltdl, boost, hdf5, optimize, warning)	11m 47s
build_linux (ubuntu-22.04, gcc, boost, optimize, warning)	13m 51s
build_linux (ubuntu-22.04, gcc, openmp, python, gsl, ltdl, boost, optimize, warning)	21m 21s
build_linux (ubuntu-22.04, gcc, mpi, python, gsl, ltdl, boost, optimize, warning)	22m 31s
build_linux (ubuntu-22.04, gcc, openmp, mpi, python, gsl, ltdl, boost, hdf5, sionlib, libneurosim...	31m 22s
	1h 57m 46s

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