added info; fixed sentence

README.md

@@ -49,7 +49,7 @@ There is no UI for the settings just yet. One way to set them until then is the
     }
 
 While Google and Heroku are pre-defined you can add arbitrary providers through configuration.
-Those will then may require the host and/or endpoints to be specified depending on whether or not a particular provider adheres to the default endpoint paths or not.
+Those may then require the host and/or endpoints to be specified depending on whether or not a particular provider adheres to the default endpoint paths or not.
 
     Setting["plugin_openproject_openid_connect"] = {
       "providers" => {
@@ -78,3 +78,5 @@ Those will then may require the host and/or endpoints to be specified depending
 
 If a host is given, relative endpoint paths will refer to said host.
 No host is required if absolute endpoint URIs are given.
+
+The configuration of the pre-defined providers (currently Google and Heroku) can be overriden as well.