Use tidytemplate

[gaborcsardi]

• [x] usethis::use_pkgdown_github_pages()
• [x] Ensure Author includes RStudio as copyright holder and funder
• [x] Update DESCRIPTION to include Config/Needs/website: tidyverse/tidytemplate
• [x] Update _pkgdown.yml with appropriate template above.
• [ ] Ping Hadley to add plausible.io record
• [x] Remove strip_header: true
• [x] Remove algolia search, if used
• [x] Eliminate superseded navbar customisation (home: ~, article re-ordering)
• [x] Update news structure if needed
• [x] Remove any author info for tidyverse folks (since now included in template)