add decimal support

Author: tanner0101

Sources/PostgreSQL/Data/PostgreSQLData+Decimal.swift

@@ -0,0 +1,23 @@
+import Core
+
+extension Decimal: PostgreSQLDataConvertible {
+    /// See `PostgreSQLDataConvertible`
+    public static var postgreSQLDataType: PostgreSQLDataType {
+        return Double.postgreSQLDataType
+    }
+
+    /// See `PostgreSQLDataConvertible`
+    public static var postgreSQLDataArrayType: PostgreSQLDataType {
+        return Double.postgreSQLDataArrayType
+    }
+
+    /// See `PostgreSQLDataConvertible`
+    public static func convertFromPostgreSQLData(_ data: PostgreSQLData) throws -> Decimal {
+        return try Decimal(Double.convertFromPostgreSQLData(data))
+    }
+
+    /// See `PostgreSQLDataConvertible`
+    public func convertToPostgreSQLData() throws -> PostgreSQLData {
+        return try Double(description).convertToPostgreSQLData()
+    }
+}