Do not support pointer to user type

[serg2014]

// use github.com/caarlos0/env/v11 v11.3.1

func TestCustomParserWIthDefault(t *testing.T) {
	type foo struct {
		name string
	}

	type bar struct {
		Name string `env:"OTHER_CUSTOM"`
		Foo  *foo   `env:"BLAH_CUSTOM"`
	}

	type config struct {
		Var   foo  `env:"VAR_CUSTOM"`
		Foo   *foo `env:"BLAH_CUSTOM"`
		Other *bar
	}

	t.Setenv("VAR_CUSTOM", "test")
	t.Setenv("OTHER_CUSTOM", "test2")
	t.Setenv("BLAH_CUSTOM", "test3")

	runtest := func(t *testing.T) {
		t.Helper()
		cfg := &config{
			Var: foo{"var"},
			Foo: &foo{"foo"},
			Other: &bar{
				Name: "name",
				Foo:  &foo{"foo"},
			},
		}
		err := ParseWithOptions(cfg, Options{FuncMap: map[reflect.Type]ParserFunc{
			reflect.TypeOf(foo{}): func(v string) (interface{}, error) {
				return foo{name: v}, nil
			},
		}})

		isNoErr(t, err)
		expect := &config{
			Var: foo{"test"},
			Foo: &foo{"test3"},
			Other: &bar{
				Name: "test2",
				Foo:  &foo{"test3"},
			},
		}
		assert.Equal(t, expect, cfg)
	}

	for i := 0; i < 10; i++ {
		t.Run(fmt.Sprintf("%d", i), runtest)
	}
}

this test is failed

 Diff:
                                --- Expected
                                +++ Actual
                                @@ -5,3 +5,3 @@
                                  Foo: (*env.foo)({
                                -  name: (string) (len=5) "test3"
                                +  name: (string) (len=3) "foo"
                                  }),
                                @@ -10,3 +10,3 @@
                                   Foo: (*env.foo)({
                                -   name: (string) (len=5) "test3"
                                +   name: (string) (len=3) "foo"
                                   })

this patch serg2014@931c721
resolve problem