doc/install: add manual RADOSGW install procedure

doc/install: add manual RADOSGW install procedure

Add a manual RADOSGW installation procedure to
doc/install/manual-deployment.rst. This procedure was developed by Janne
Johansson and reported to the ceph-users mailing list on 29 Jan 2024
here: https://lists.ceph.io/hyperkitty/list/ceph-users@ceph.io/message/LB3YRIKAPOHXYCW7MKLVUJPYWYRQVARU/

Co-authored-by: Janne Johansson <icepic.dz@gmail.com>
Co-authored-by: Anthony D'Atri <anthony.datri@gmail.com>
Signed-off-by: Zac Dover <zac.dover@proton.me>