Fix links in README and add ropensci CoC

[BatoolMM]

Closes #215 #216

Proposed Changes

• Fix all links to the GitHub repo to point to the repo under the ropensci organisation
• Add ropensci CoC
• Add installation instructions through r-universe

Checklist for the author of this PR:

• [if package files were edited] I have run these checks locally:
  • devtools::document() to generates the .Rd files from any updated roxygen comments.
  • lintr::lint_package(path = ".") to check for style compliance and syntax issues.
  • codemetar::write_codemeta() to ensures the metadata file is up to date.
  • devtools::check() for a comprehensive package check. I have resolved any warnings or errors, or written them here in the PR, for discussion.
• The code base and the documentation files match (they both reflect any recent changes).
• The title of this PR is clear and self-explantory.
• I have added any appropriate labels to this PR.
• This PR is now ready for review (and I have removed the draft PR status).

[RayStick]

Thanks for working on this Batool!