docs: document local dev dependencies (#1147)

README.md

@@ -164,6 +164,30 @@ To install development dependencies run:
 $ make install-dev
 ```
 
+## Local development
+
+Your local machine needs:
+
+* Docker
+* Python
+
+`make lock` requires GDAL and Cython:
+
+```sh
+$ brew install gdal
+```
+
+```sh
+$ apt install gdal
+```
+
+### cython
+
+```sh
+$ pip3 install cython
+```
+
+
 ## Generating GraphQL public documentation
 
 The API docs are generated by