Many fonts on Typekit support French. You can browse fonts that support French by selecting "French" from the list of supported languages in the sidebar under browse fonts.
French is included in the default option, so the French characters will be available to your website within a few minutes of publishing your kit.
You may also create a custom language subset which includes French, to reduce the size of your kit. The Language Support & Subsetting help page has more information on the character set options.
All fonts that support French include the following letter characters, at minimum: