add test badge & RTD yaml config

Author: rmnldwg

.readthedocs.yml

@@ -0,0 +1,25 @@
+# .readthedocs.yml
+# Read the Docs configuration file
+# See https://docs.readthedocs.io/en/stable/config-file/v2.html for details
+
+# Required
+version: 2
+
+build:
+  os: ubuntu-22.04
+  tools:
+    python: "3.10"
+
+# Build documentation in the docs/ directory with Sphinx
+sphinx:
+  builder: html
+  configuration: docs/source/conf.py
+  fail_on_warning: false
+
+# tell RTD to install the package with the docs optional requirements
+python:
+  install:
+    - method: pip
+      path: .
+      extra_requirements:
+        - docs

README.md

@@ -78,6 +78,8 @@ Besides the data, this repository provides a Python library for loading, manipul
 > [!CAUTION]
 > This Python library is still highly experimental!
 
+[![Tests](https://github.com/rmnldwg/lydata/actions/workflows/tests.yml/badge.svg)](https://github.com/rmnldwg/lydata/actions/workflows/tests.yml)
+
 If you want to install this library, clone the repo and install it. You can do so by executing these commands:
 
 ```bash