Add section to readme

README.md

@@ -12,6 +12,7 @@ Rust bindings and SDK for the ELSTER Rich Client (ERiC)
 - [What is ERiC?](#what-is-eric)
 - [Requirements](#requirements)
 - [Rust bindings](#rust-bindings)
+  - [Select bindings](#select-bindings)
   - [Generate bindings](#generate-bindings)
   - [Test bindings](#test-bindings)
 - [Eric SDK](#eric-sdk)
@@ -34,6 +35,8 @@ You need to have the shared library `libericapi.so` and the header file `ericapi
 
 ## Rust bindings
 
+### Select bindings
+
 The bindings are selected from the pre-generated bindings by specifying the
 environment variables `PATH_VENDOR`, `LIBRARY_NAME`, `LIBRARY_PATH`, `HEADER_FILE`, and
 `PLUGIN_PATH`. For example: