As much I'd love it if this was true, Stormy Daniels suing Donald Trump is not grounds for impeachment. The Constitution sets specific grounds for impeachment. They are “treason, bribery, and other high crimes and misdemeanors.” To be impeached and removed from office, the House and Senate must find that the president committed one of these acts.
Stormy Daniels is by no means the first to sue Donald Trump, nor will she likely be the last. And the thing that she's actually suing Trump for isn't really a crime- she's only suing him over holes in their 'hush' agreement. Not exactly "treason, bribery, [or]... [a] high crime/misdemeanor."
Besides, even if it was, it's not really easy to impeach to a president. Only two presidents ever in American History have been impeached (Andrew Johnson and Bill Clinton; Nixon resigned before he could be impeached) and the process for impeachment is not an easy feat, especially given our modern day political climate. Here's what would have to happen in order to impeach Trump:
1. The House Judiciary Committee holds hearings and, if necessary, prepares articles of impeachment. These are the charges against the official.
2. If a majority of the committee votes to approve the articles, the whole House debates and votes on them.
3. If a majority of the House votes to impeach the official on any article, then the official must then stand trial in the Senate.
4. For the official to be removed from office, two-thirds of the Senate must vote to convict the official. Upon conviction, the official is automatically removed from office and, if the Senate so decides, may be forbidden from holding governmental office again.
And, unfortunately, there is almost nothing that Trump could do to persuade a Republican-majority Congress to impeach the leader of their party. Maybe things will be different if you vote Democrat in November. ¯\_(ツ)_/¯
See the source provided for more details on impeachment.