feat: add support of xcstrings file type by files-api (#124)

Author: dnetrebenko-smartling

smartling-files-api/src/main/java/com/smartling/api/files/v2/pto/FileType.java

@@ -48,7 +48,8 @@ public enum FileType
     XLIFF2("application/xml", false),               // XLIFF 2.0 parser
     ARB("application/json", false),                 // ARB parser
     NONE("application/octet-stream", false),        // No content files associated with this type, used for strings-api
-    XLSX_TEMPLATE("application/octet-stream", false);        // Smartling XLSX - https://help.smartling.com/hc/en-us/articles/1260804224670-Translating-Spreadsheets#h_01F3TKVZBVPFJSF2XZEBHDH1EQ
+    XLSX_TEMPLATE("application/octet-stream", false),        // Smartling XLSX - https://help.smartling.com/hc/en-us/articles/1260804224670-Translating-Spreadsheets#h_01F3TKVZBVPFJSF2XZEBHDH1EQ
+    XCSTRINGS("application/json", true);            // iOS String Catalog - https://help.smartling.com/hc/en-us/articles/31159241673627-iOS-String-Catalog
     private final String identifier;
     private final String mimeType;
     private final boolean isTextFormat;