Create CONTRIBUTING.md

[jgabry]

Adds CONTRIBUTING.md based on the tidyverse contributing guidelines

[codecov-commenter]

Codecov Report

Merging #311 (3fb442c) into master (60dbbe9) will not change coverage.
The diff coverage is n/a.

❗ Current head 3fb442c differs from pull request most recent head fc68364. Consider uploading reports for the commit fc68364 to get more accurate results

@@           Coverage Diff           @@
##           master     #311   +/-   ##
=======================================
  Coverage   95.60%   95.60%           
=======================================
  Files          47       47           
  Lines        3686     3686           
=======================================
  Hits         3524     3524           
  Misses        162      162           

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[github-actions]

This is how benchmark results would change (along with a 95% confidence interval in relative change) if 3fb442c is merged into master:

•   :ballot_box_with_check:as_draws_array: 104ms -> 103ms [-1.48%, +0.93%]
•   :ballot_box_with_check:as_draws_df: 32.5ms -> 32.5ms [-2%, +2.09%]
•   :ballot_box_with_check:as_draws_list: 191ms -> 193ms [-0.55%, +2.33%]
•   :rocket:as_draws_matrix: 33.2ms -> 29.8ms [-17.58%, -2.45%]
•   :ballot_box_with_check:as_draws_rvars: 164ms -> 161ms [-4.69%, +0.89%]
•   :ballot_box_with_check:summarise_draws_100_variables: 720ms -> 715ms [-1.78%, +0.22%]
•   :ballot_box_with_check:summarise_draws_10_variables: 79.8ms -> 79.9ms [-0.91%, +1.37%]
  Further explanation regarding interpretation and methodology can be found in the documentation.

[paul-buerkner]

Looks good to me. Thanks! Do you want to make any changes before merging?

[jgabry]

Looks good to me. Thanks! Do you want to make any changes before merging?

Thanks. I think it's good to go. Will merge now.