Add Posit Workbench QA tests

[shikokuchuo]

QA tests included in the dev repo folder, which is not part of the R package itself.

Instructions:

1. Install dev mirai

Rscript -e 'pak::pak("r-lib/mirai")'

2. Run tests (replace with location of test file - it's not part of the package itself)

Rscript -e 'testthat::test_file("dev/tests/test-mirai-workbench.R")'