DOC: Mention gitpod as alternative in environment setup docs (#21255)
DOC: Mention gitpod as alternative in environment setup docs (#21255)

* DOC: mention Gitpod as alternative to build numpy

Fixes #20679

Co-authored-by: Ross Barnowski <e9fb290bfd0a4406872fd6103425d9efafcfa051@berkeley.edu>
pdebuyl/numpy,pdebuyl/numpy,mattip/numpy,jakirkham/numpy,rgommers/numpy,mhvk/numpy,mhvk/numpy,endolith/numpy,seberg/numpy,endolith/numpy,seberg/numpy,charris/numpy,rgommers/numpy,jakirkham/numpy,rgommers/numpy,jakirkham/numpy,numpy/numpy,pdebuyl/numpy,mattip/numpy,anntzer/numpy,charris/numpy,pdebuyl/numpy,numpy/numpy,mattip/numpy,numpy/numpy,anntzer/numpy,jakirkham/numpy,seberg/numpy,rgommers/numpy,seberg/numpy,mhvk/numpy,endolith/numpy,charris/numpy,jakirkham/numpy,mattip/numpy,mhvk/numpy,mhvk/numpy,anntzer/numpy,charris/numpy,endolith/numpy,anntzer/numpy,numpy/numpy