added embedded prolog example

package ai

package ai

import (

	_ "embed"

	"testing"

	"github.com/ichiban/prolog"

)

var (

	//go:embed example.pl

	example string

)

func TestProlog(t *testing.T) {

	p := prolog.New(nil, nil)

	if err := p.Exec(example); err != nil {

		t.Fatalf("prolog.Exec() failed with: %s", err)

	}

	sols, err := p.Query(`mortal(Who).`)

	if err != nil {

		t.Fatalf("p.Query() failed with: %s", err)

	}

	defer sols.Close()

	for sols.Next() {

		var s struct {

			Who string

		}

		if err := sols.Scan(&s); err != nil {

			t.Errorf("prolog.solutions.Scan() failed with: %s", err)

		}

		t.Logf("Who = %s", s.Who)

	}

}

human(socrates).       % This is a fact.

mortal(X) :- human(X). % This is a rule.