[Google Play Books Store API] Typo in example JSON

[chukhraiartur]

There is a typo in the documentation example:

Current key name:

"extansion": {
    # some data
},

Expected key name:

"extension": {
    # some data
},

Link to Documentation: https://serpapi.com/google-play-books

[sebastianquek]

@chukhraiartur Thanks for raising this issue. Both the documentation and the actual output JSON have been updated to use the "extension" key.