Add developer section to README (#889)

README.md

@@ -86,12 +86,38 @@ to install the default SSSP version.
 List the installed pseudopotential families with the command `aiida-pseudo list`.
 You can then use the name of any family in the command line using the `-F` flag.
 
+## Development
+
+### Running tests
+To run the tests, simply clone and install the package locally with the [tests] optional dependencies:
+
+```shell
+git clone https://github.com/aiidateam/aiida-quantumespresso .
+cd aiida-quantumespresso
+pip install -e .[tests]  # install extra dependencies for test
+pytest # run tests
+```
+
+You can also use `tox` to run the test set. Here you can also use the `-e` option to specify the Python version for the test run:
+```shell
+pip install tox
+tox -e py39 -- tests/calculations/test_pw.py
+```
+
+### Pre-commit
+To contribute to this repository, please enable pre-commit so the code in commits are conform to the standards.
+Simply install the repository with the `pre-commit` extra dependencies:
+```shell
+cd aiida-quantumespresso
+pip install -e .[pre-commit]
+pre-commit install
+```
 
 ## License
 The `aiida-quantumespresso` plugin package is released under the MIT license.
 See the `LICENSE.txt` file for more details.
 
-## Acknowlegements
+## Acknowledgements
 We acknowledge support from:
 * the [NCCR MARVEL](http://nccr-marvel.ch/) funded by the Swiss National Science Foundation;
 * the EU Centre of Excellence "[MaX – Materials Design at the Exascale](http://www.max-centre.eu/)" (Horizon 2020 EINFRA-5, Grant No. 676598; H2020-INFRAEDI-2018-1, Grant No. 824143; HORIZON-EUROHPC-JU-2021-COE-1, Grant No. 101093324);