Put your heart into making a difference.    February is Heart Month in Manitoba, when volunteers go door-to-door to raise money and share the risks and warning signs of heart disease and stroke.   Since it's inception in 1957, the Heart & Stroke Foundation of Manitoba has given almost $55 million to research.   They are now recognized as a major authority on heart disease and stroke, and have helped cut premature deaths from both conditions by 50 per cent through their programs.   To help with the Thompson and Area campaign, contact Al Meston at 778-89-88.