Update README about inline references

fixes #122

Author: cebe

README.md

@@ -195,9 +195,20 @@ references to structures in external files, we must provide the full context.
 
 ```php
 use cebe\openapi\Reader;
+use cebe\openapi\spec\OpenAPI;
+use cebe\openapi\ReferenceContext;
+
+// there are two different modes for resolving references:
+// ALL: resolve all references, which will result in a large description with a lot of repetition
+// but no references (except if there are recursive references, these will stop at some level)
+$mode = ReferenceContext::RESOLVE_MODE_ALL;
+// INLINE: only references to external files are resolved, references to places in the current file
+// are still Reference objects.
+$mode = ReferenceContext::RESOLVE_MODE_INLINE;
+
 // an absolute URL or file path is needed to allow resolving external references
-$openapi = Reader::readFromJsonFile('https://www.example.com/api/openapi.json');
-$openapi = Reader::readFromYamlFile('https://www.example.com/api/openapi.yaml');
+$openapi = Reader::readFromJsonFile('https://www.example.com/api/openapi.json', OpenAPI::class, $mode);
+$openapi = Reader::readFromYamlFile('https://www.example.com/api/openapi.yaml', OpenAPI::class, $mode);
 ```
 
 If data has been loaded in a different way you can manually resolve references like this by giving a context: