Merge pull request #338 from Open-Telecoms-Data/0.4-release

changelog: Update 0.4 release date

schema: Update old docs URLs

schema/network-schema.json: Fix typo in version placeholders

Update build directory and schema paths

.readthedocs.yaml: Fail on Sphinx warnings

.readthedocs.yaml: Update Ubuntu to 22.04

docs/primer/scopeandkeyconcepts.md: Update schema URL

.github/workflows: Remove sphinx-bulid, in favour of building on readthedocs

trigger build

docs/conf.py: Print output directory

conf.py: Print outdir

Update version numbers and schema URLs

docs/conf.py: Copy network package schema and codelists to output directory

docs/conf.py: Use app.outdir