DOC: add JOSS link to README.rst [skip ci][ci skip]
DOC: add JOSS link to README.rst [skip ci][ci skip]

also updated the Zenodo badge to point to link to the most recent release
instead of 1.0.0 specifically.

grlee77/pywt,rgommers/pywt,PyWavelets/pywt,PyWavelets/pywt,rgommers/pywt,rgommers/pywt,grlee77/pywt,rgommers/pywt