Fix example syntax

Author: valeriansaliou

README.md

@@ -183,7 +183,7 @@ Vigil will be reachable from `http://localhost:8080`.
 
 Use the sample [config.cfg](https://github.com/valeriansaliou/vigil/blob/master/config.cfg) configuration file and adjust it to your own environment.
 
-You can also use environment variables with string interpolation in your configuration file, eg. `manager_token: ${VIGIL_MANAGER_TOKEN}`.
+You can also use environment variables with string interpolation in your configuration file, eg. `manager_token = ${VIGIL_MANAGER_TOKEN}`.
 
 **Available configuration options are commented below, with allowed values:**