Update README.md

Added Hash Option Explanation

README.md

@@ -102,7 +102,7 @@ For NUnit we will support the Assert.That syntax (Coming soon):
 
 ## Features
 
-### Ignore Fields in Snapshots Matches
+### Ignore Fields in Snapshots
 
 If some fields in your snapshot shall be ignored during snapshot assertion, then the following ignore options can be used:
 
@@ -157,7 +157,57 @@ Option 2: Use the default ignore match option 'IgnoreFields(**.<fieldName>)' wit
 Snapshot.Match<Person>(person, matchOptions => matchOptions.IgnoreFields("**.Id"));
 ```
 
-### Assert Fields in Snapshots Matches
+### Hash Fields in Snapshots
+
+If some fields of our snapshot are too big, for example a binary field with a lot of data, then we can use the HashField option.
+The HashField option creates a Hash of the field value and therefore each time only the hash is compared. 
+If there is a change in the field value, then the snapshot match will fail.
+
+```csharp
+[Fact]
+public void ImageSnapshot_HashImageBinary()
+{
+ // arrange
+ var serviceClient = new ServiceClient();
+
+ // act
+ TestImage image = serviceClient.CreateMonaLisaImage();
+
+ // assert
+ Snapshot.Match(image, matchOptions => matchOptions.HashField("Data"));
+}
+```
+Example Snapshot with Hash
+```json
+{
+ "Id": 3450987,
+ "OwnerId": "0680faef-6e89-4d52-bad8-291053c66696",
+ "Name": "Mona Lisa",
+ "CreationDate": "2020-11-10T21:23:09.036+01:00",
+ "Price": 951868484.345,
+ "Data": "m+sQR9KG9WpgYoQiRASPkt9FLJOLsjK86UuiXKVRzas=" 
+}
+```
+
+The field(s) to hash can be located via JsonPath or via field name.
+
+Hash Field Examples:
+
+```csharp
+// Hash the field 'Data' of the child node 'Thumbnail' of the person
+Snapshot.Match<Person>(person, matchOptions => matchOptions.HashField("Thumbnail.Data"));
+
+// Hash the field 'Data' of the first thumbnail in the 'Thumbnails' array of the image
+Snapshot.Match<Person>(person, matchOptions => matchOptions.HashField("Thumbnails[0].Data"));
+
+// Ignores the field 'Data' of all 'Thumbnails' nodes of the image
+Snapshot.Match<Person>(person, matchOptions => matchOptions.HashField("Thumbnails[*].Data"));
+
+// Ignores all fields with name 'Data'
+Snapshot.Match<Person>(person, matchOptions => matchOptions.HashField("**.Data"));
+```
+
+### Assert Fields in Snapshots
 
 Sometimes there are fields in a snapshot, which you want to assert separately against another value.