Use apt to provide sphinx and improve the workflow #115

	name: Build documentation

	permissions:
	contents: read

	on:
	push:
	pull_request:
	types: [opened, synchronize, reopened]
	branches:
	- master

	jobs:
	build-docs:
	name: Build the documentation
	runs-on: ubuntu-latest
	steps:
	- uses: actions/checkout@v3
	with:
	submodules: true
	- name: Install Sphinx
	run: sudo apt install sphinx-doc
	- name: Install gettext
	run: sudo apt-get install -y gettext
	- name: Build the documentation
	run: make html SPHINXOPTS='-n -W -a'
	- name: Build the documentation and show all errors
	if: ${{ failure() }}
	# This mode will not exit on the first error and will display all of them
	run: make html SPHINXOPTS='-n -a'

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