Add contribution guidelines

Author: daniel-jones-dev

CHANGELOG.md

@@ -7,6 +7,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 ### Added
+* Add contribution guidelines -- currently we are unable to accept Pull Requests.
 ### Changed
 * Improve README.
 ### Deprecated

CONTRIBUTING.md

@@ -0,0 +1,4 @@
+# Contribution guidelines
+
+We are currently unable to accept Pull Requests. If you would like to suggest changes, please open an
+[issue](https://github.com/DeepLcom/deepl-python/issues) instead.

README.md

@@ -159,8 +159,15 @@ python3 -m deepl --auth-key=YOUR_AUTH_KEY text --to=DE "Text to be translated."
 ```
 Wrap text arguments in quotes to prevent the shell from splitting sentences into words.
 
+## Issues
+
+If you experience problems using the library, or would like to request a new feature, please open an
+[issue](https://www.github.com/DeepLcom/deepl-python/issues). 
+
 ## Development
 
+We are currently unable to accept Pull Requests. If you would like to suggest changes, please open an issue instead.
+
 ### Tests 
 
 Execute the tests using `pytest`. The tests communicate with the DeepL API using the auth key defined by the
@@ -172,7 +179,3 @@ only with the DeepL API or the mock-server and will be otherwise skipped.  The t
 trigger server errors and test the client error-handling. To execute the tests using deepl-mock, run it in another
 terminal while executing the tests. Execute the tests using `pytest` with the `DEEPL_MOCK_SERVER_PORT` and
 `DEEPL_SERVER_URL` environment variables defined referring to the mock-server.
-
-### Issues
-If you experience problems using the library, or would like to request a new feature, please create an
-[issue](https://www.github.com/DeepLcom/deepl-python/issues).