You can create a SP Designer workflow to do this. Research some examples of using the Call HTTP web service action in SP Designer for more specifics, but here is a summary:
Call HTTP Web Service (HTTP Get) to your list, example
HTTP web service URL: yoursite/_api/web/lists/GetByTitle('Posts')/Items?$select=LikesCount,LikedBy/Title&$expand=LikedBy&$filter=Title eq ('Title*')
Title*= set equal to current item title
Then Get Item from Dictionary: Get (0)/LikedBy/results output to another dictionary variable (LikedByDic).
Count items in above step and then create Loop to run through the second dictionary.
Within the Loop, Get (CountVariableUsedInLoop)/Title from the second dictionary (LikedByDic) output to string variable(UserLikedBy)(this will be the user who liked the post).
I created another string variable (AllUsers) within the loop to add each user:
Set Variable: AllUsers to [%Variable:UserLikedBy%];[%Variable:AllUsers%]
Then a final step after the loop stage to email me the value of this string variable (AllUsers).