GH action re-knit README after changes in blazr features

[jibarozzo]

Improve rendering of README to capture changes to blazr features and functionalities. It would be great to re-knit after updates to package and include examples.

    This is awesome, but just a note here:

RMD_PATH=$(git diff --name-only ${{ github.event.before }} ${{ github.sha }} | grep '\.Rmd$' || true)

This bash command will run a git diff and grep any .Rmd files that have been changed before/ after the PR. While that will catch any direct changes to the .Rmd itself, it won't catch underlying changes in the blazr package.

So for example, if we were to update the functionality of a blazr function but didn't make any changes to the README, this action wouldn't catch those changes, and wouldn't try to trigger a re-knit of the README.Rmd.

Certainly not a blocking comment to this PR, but maybe something worth expanding on at a later date to improve the action

Originally posted by @jdhoffa in #17 (comment)