You don't need to add more yeast. At any given time towards the end of a primary fermentation, there are literally hundreds of millions of yeast in your fermentor. When you rack to your bottling bucket and bottle, you still have tens of millions of yeast in suspension, even when most of them are left behind on the yeast cake. Once you add your priming sugar to the bottled solutions, you now still have millions of yeast in each bottle, which will then multiply once they start eating the priming sugar and producing your CO2 carbonation.
Unless you are coming out of a stuck fermentation or some other type of fermentation issue, you do not need to add extra yeast.