You can add Tom Petty’s name to the list of people playing at Fenway Park this summer. The rocker tweeted a picture of the ballpark Monday with the caption “Coming Soon . . . ,” confirming a rumor we’d heard that he and the Heartbreakers might be the third headliner of the summer. (Billy Joel plays at Fenway June 26 and Zac Brown and his band perform on June 27 and 28.) Neither Live Nation nor Fenway officials have announced the date of the Petty show, but we’re told it’ll be Aug. 30 — and a second show could be added if there’s sufficient demand. The Red Sox will be playing the Rays in Tampa.