docs: creation of basic structure

initial adding of config (based on pmb/docs)

.ci/docs.sh

+#!/bin/sh -e
+# Description: create documentation with sphinx
+# Artifacts: public/
+# https://postmarketos.org/pmb-ci
+
+
+# Install sphinx + extensions when running in CI
+if [ "$(id -u)" = 0 ]; then
+	set -x
+	apk -q add \
+		py3-flask \
+		py3-myst-parser \
+		py3-sphinx_rtd_theme \
+		py3-sphinxcontrib-autoprogram \
+		py3-sqlalchemy
+	exec su "${TESTUSER:-build}" -c "sh -e $0"
+fi
+
+# Validate that all modules are documented.
+fail=0
+modules="$(find bpo/ -name "*.py" | grep -v '/__init__.py' | sort | sed 's|\.py$||' | sed 's|/|.|g')"
+for module in $modules; do
+	if ! grep -q "automodule:: $module" docs/api/*.rst; then
+		echo "Undocumented module: $module"
+		fail=1
+	fi
+done
+if [ "$fail" -eq 1 ]; then
+	echo "ERROR: Found undocumented modules!"
+	echo "ERROR: Please add this module to the correct .rst file in docs/"
+	exit 1
+fi
+
+sphinx-build \
+	docs \
+	public \
+
+#	-E -a -v -T