Created Better UUID and Numeric Types (markdown)

Better-UUID-and-Numeric-Types.md

@@ -0,0 +1,36 @@
+The Go standard library does not have types directly corresponding to PostgreSQL `uuid` and `numeric`. 3rd party libraries are available but pgx does not use them by default to avoid external dependencies.
+
+However, pgx supports both the ability to register new data types and to override the default handling of currently supported types. There are packages available to use `github.com/gofrs/uuid` and `github.com/shopspring/decimal`.
+
+Import the following packages:
+
+```go
+import (
+	pgtypeuuid "github.com/jackc/pgtype/ext/gofrs-uuid"
+	shopspring "github.com/jackc/pgtype/ext/shopspring-numeric"
+)
+```
+
+Then register the data types for your connection. If you are using a connection pool this should be done in the `AfterConnect` hook.
+
+```go
+dbconfig, err := pgxpool.ParseConfig(databaseURL)
+if err != nil {
+	// handle error
+}
+dbconfig.AfterConnect = func(ctx context.Context, conn *pgx.Conn) error {
+	conn.ConnInfo().RegisterDataType(pgtype.DataType{
+		Value: &pgtypeuuid.UUID{},
+		Name:  "uuid",
+		OID:   pgtype.UUIDOID,
+	})
+	conn.ConnInfo().RegisterDataType(pgtype.DataType{
+		Value: &shopspring.Numeric{},
+		Name:  "numeric",
+		OID:   pgtype.NumericOID,
+	})
+
+	return nil
+}
+```
+