GitLab

* improve experience with optional GitHub workflows

* Update README.md

* Update r_artifacts.yml

* Update optional_checks.yml

* continue

* Update triggering_comments.yml

* Update README.md

* Update r_artifacts.yml

* Update r_artifacts.yml

* Update r_artifacts.yml

* Update r_valgrind.yml

* Update r_artifacts.yml

* Update r_valgrind.yml

* Update r_valgrind.yml

* Update r_valgrind.yml

* add docstrings to fix lint

* better formatting for multi-line commands

* [ci] upgrade GitHub Actions third-party actions to newest versions

* add git to sanitizers container

* install git before checkout

* Update .github/workflows/r_package.yml
Co-authored-by: Nikita Titov <nekit94-08@mail.ru>
Co-authored-by: Nikita Titov <nekit94-08@mail.ru>

* [ci] automate building CRAN package

* add workflow for building CRAN package

* remove newlines

* add to R README

* Apply suggestions from code review
Co-authored-by: Nikita Titov <nekit94-08@mail.ru>

* add timeout
Co-authored-by: Nikita Titov <nekit94-08@mail.ru>