Decode nil for single or keyed values if value is 'NA' or 'N/A'

Sources/CSV/Coder/Decoder/_CSVKeyedDecoder.swift

@@ -18,7 +18,8 @@ final class _CSVKeyedDecoder<K>: KeyedDecodingContainerProtocol where K: CodingK
     }
     
     func decodeNil(forKey key: K) throws -> Bool {
-        return row[key.stringValue] == nil
+        let cell = row[key.stringValue]
+        return cell == nil || cell == Data([.N, .forwardSlash, .A]) || cell == Data([.N, .A])
     }
     
     func decode(_ type: Bool.Type, forKey key: K) throws -> Bool {

Sources/CSV/Coder/Decoder/_CSVSingleValueDecoder.swift

@@ -11,7 +11,9 @@ final class _CSVSingleValueDecoder: SingleValueDecodingContainer {
         self.value = value
     }
     
-    func decodeNil() -> Bool { return self.value == nil }
+    func decodeNil() -> Bool {
+        return value == nil || value == Data([.N, .forwardSlash, .A]) || value == Data([.N, .A])
+    }
     
     func decode(_ type: Bool.Type) throws -> Bool {
         guard let cell = self.value else { throw DecodingError.nilValue(type: type, at: self.codingPath) }