Updated Implementing formats with ol.format.Format (markdown)

Implementing-formats-with-`ol.format.Format`.md

@@ -12,4 +12,10 @@ The IGC format contains only one feature per file, so `readFeature` returns that
 
 For formats that only contain a single geometry, like WKB and WKT, `readGeometry` should return that geometry, `readFeature` should return a feature with its geometry set to the geometry read from the file, and `readFeatures` should return an array containing the single feature returned by `readFeature`.
 
-If a file cannot be parsed, then the return value should be `null` for all three cases. Parsing failures should not raise exceptions (although exceptions can be used internally).
+If a file cannot be parsed, then the return value should be `null` for all three cases. Parsing failures should not raise exceptions (although exceptions can be used internally).
+
+## Handling errors
+
+There are an infinite number of ways that data can not meet a specification. It would be an endless battle to try to enumerate and return error messages for each and every single one of them. Formats with multiple features might contain a mix of correctly-formed and malformed features. Should an error be returned in this case?
+
+`ol.format.Format` that it should read as many features as it can, skipping features with any errors.