create a trigger in mindsdb to retrain the model every time data is updated after receiving pull request closed event

[vishesh-baghel]

ref: https://docs.mindsdb.com/sql/create/trigger

[vishesh-baghel]

As of now, it is not possible to achieve what I am trying to implement in the bot. The trigger in the mindsDB will simply fetch all the columns from the collection to update the 'files' collection in MongoDB. I have added the feature to retrain the predictor model on every update in the PR for #6