Add support for .meta.json files affecting .csv LocalizationTables

src/snapshot_middleware/snapshots/test__csv_from_imfs.snap

@@ -9,6 +9,7 @@ metadata:
     Path: /foo.csv
   relevant_paths:
     - /foo.csv
+    - /foo.meta.json
 name: foo
 class_name: LocalizationTable
 properties:

src/snapshot_middleware/snapshots/test__csv_with_meta.snap

@@ -0,0 +1,19 @@
+---
+source: src/snapshot_middleware/csv.rs
+expression: instance_snapshot
+---
+snapshot_id: ~
+metadata:
+  ignore_unknown_instances: true
+  instigating_source:
+    Path: /foo.csv
+  relevant_paths:
+    - /foo.csv
+    - /foo.meta.json
+name: foo
+class_name: LocalizationTable
+properties:
+  Contents:
+    Type: String
+    Value: "[{\"key\":\"Ack\",\"example\":\"An exclamation of despair\",\"source\":\"Ack!\",\"values\":{\"es\":\"¡Ay!\"}}]"
+children: []