A couple who learned about the problem of wobbly tables first hand while working in the foodservice business are now marketing a solution.   Jamie and Brenda Cooling have formed Steady Eddie Ltd. To sell table stabilizer, no-slide rubber wedges that slip unobtrusively under table legs – a much more satisfactory solution than folded napkins, or match books and easier to use than special table feet.   The Coolings have signed up Danbro Restaurant Equipment Representatives of Bramalea as their sales agent. Jamie Cooling has more than 15 years experience in the food-service business. He works for Tricon Restaurants as area manager for 15 Pizza Huts. Brenda worked for a number of years for TCBY yogurt chain