[FEATURE] Add a function for averages

[roysti10]

Describe the issue
We would like to add statistics such as batting average, bowling average to our dataset

Solution
To do this , we would like you to add two functions in a file called average.py, batting
_average and bowling_average, and implement them.

Test
run both of them and check if it updates the dataset

Note: While making a PR dont send it in with the updated dataset, that will be done by the maintainers only, just write the functions in the file as of now

Comment if you would like to work on it

[abhisinha2001]

Can I please take this up?

[roysti10]

Yea sure! assigning it to @abhisinha2001