Merge "Ubuntu: add documentation & release note"

doc/source/administration/overcloud.rst

doc/source/administration/seed.rst

doc/source/configuration/reference/bifrost.rst

doc/source/configuration/reference/hosts.rst

doc/source/configuration/reference/index.rst

doc/source/configuration/reference/ironic-python-agent.rst

doc/source/configuration/reference/kolla.rst

doc/source/configuration/reference/network.rst

doc/source/configuration/reference/os-distribution.rst

doc/source/configuration/scenarios/all-in-one/index.rst

doc/source/configuration/scenarios/all-in-one/overcloud.rst

doc/source/contributor/automated.rst

doc/source/deployment.rst

doc/source/installation.rst

doc/source/resources.rst

doc/source/support-matrix.rst

releasenotes/notes/ubuntu-e74f49ea72f69869.yaml