readthedocs: Add configuration file

Use the more powerful configuration file .readthedocs.yaml to ensure
that all requirements are installed. This now includes also a distro
package, python-newt, something that cannot be installed via a
requirements.txt.

Fixes the doc build for 2.6.x which become broken with the addition of
the menu plugin.

Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>

.readthedocs.yaml

@@ -0,0 +1,39 @@
+# kas - setup tool for bitbake based projects
+#
+# Copyright (c) Siemens AG, 2021
+#
+# Permission is hereby granted, free of charge, to any person obtaining a copy
+# of this software and associated documentation files (the "Software"), to deal
+# in the Software without restriction, including without limitation the rights
+# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+# copies of the Software, and to permit persons to whom the Software is
+# furnished to do so, subject to the following conditions:
+#
+# The above copyright notice and this permission notice shall be
+# included in all copies or substantial portions of the Software.
+#
+# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+# SOFTWARE.
+
+version: 2
+
+build:
+  os: ubuntu-20.04
+  tools:
+    python: "3.9"
+  apt_packages:
+    - python3-newt
+
+python:
+  install:
+    - method: setuptools
+      path: .
+    - requirements: docs/requirements.txt
+
+sphinx:
+  configuration: docs/conf.py

docs/requirements.txt

@@ -1,4 +1,3 @@
 sphinx>=1.2.0
 CommonMark>=0.5.6
 sphinx-argparse>=0.2.1
-jsonschema>=2.5.0