Migration cleanup

[hypebright]

Migration cleanup: GitLab → GitHub, roxygen2 8.1.0, group badges

Will close #6

📘 What is this PR about?

Consistency/cleanup from GitLab → GitHub migration and the split of ROvis.table out of the ROvis monolith:

• README: fixed the duplicated full-sentence heading, filled in the real Description/Usage (was TBD), switched install instructions from devtools::install_gitlab() to remotes::install_github(), removed internal gitlab.rivm.nl links, and pointed Support/Contributing/License at the SPIN (vs DARA) team contact and community files.
• CODE_OF_CONDUCT.md: contact changed from the old DARA team to SPIN team.
• Removed the stray leftover .gitlab-ci.yml from the pre-GitHub setup.
• Vignette: added vignettes/getting-started.qmd (very basic ro_gt_theme() and ro_dt_table()/ro_dt_theme() examples).
• NEWS.md: added the v0.1.0 entry. DESCRIPTION version bumped to match.
• roxygen2 8.1.0: standardized DESCRIPTION on Config/roxygen2/markdown + Config/roxygen2/version. Also fixed a malformed multi-line @importFrom that had accidentally split tab_style into two tokens, tolerated by older roxygen2 but rejected by 8.1.0 + a typo importing a non-existent systemfonts() function instead of system_fonts().
• Group badges: added man/figures/group-gt.svg and group-DT.svg (colors match ROvis.table's own hex sticker)

Depends on github-files being merged into develop first. This branch was built on top of it (for the community files), so its diff will only be clean once that's in.

✅ Checklist

• I have read contributing guidelines at CONTRIBUTING.md
• My code follows the style guidelines of this project
• I have tested these changes and added tests (if applicable)
• I have added necessary documentation / comments
• I have linked relevant issues

🧪 How to test / verify

devtools::document()
devtools::test()
devtools::check()
# Confirm badges render:
?ro_gt_theme
?ro_dt_table

ℹ️ Extra info

devtools::check() is clean (0 errors, 0 warnings). The one remaining NOTE ("Non-standard file/directory found at top level: 'CONTRIBUTORS.md'") is expected. Need to discuss.

[hypebright]

@Sjonnie404 pretty much identical to rivm-syso/ROvis.utils#3

[Sjonnie404]

@hypebright all looks nice!
All test pass
Check gave no issues (only the single note)

❯ checking top-level files ... NOTE
Non-standard file/directory found at top level:
‘CONTRIBUTORS.md’

All mentioned changes have been implemented.

---

I have one minor question:
We've added back Config/roxygen2/markdown to the description, but shouldn't this quarto instead?
I see that we've added it everywhere, but not sure if its correct.

[Sjonnie404]

See comment in PR