Add render-rmarkdown.yml GH workflow (#221)

[tomjemmett]

Recreating @francisbarton PR (#221) as there were issues running the actions

• Export S3 methods in to_datetime.R

• Edit test file to avoid lintr error

• Add render-rmarkdown.yml GH Action

• Update README.Rmd

• Update render-rmarkdown.yml

• Merge branch 'render_rmd2'

• Try to avoid lintr error

• remove the renv step from render-rmarkdown.yml

• Update render-rmarkdown.yml

• Replace magrittr pipe with base pipe in README

• Add manual workflow dispatch to render-rmarkdown

• Update render-rmarkdown.yml

• Try to fix README render workflow code

• quote filename!

• Add git add line to Rmd render workflow script

• Re-build Rmarkdown files

• Update README.Rmd

• Re-build Rmarkdown files

• Use dev version of PTD to generate charts in README

• Add chunk labels to README where missing

• Regenerate README charts

• Update R-CMD-check.yaml to use checkout@v4

• Update pkgdown.yaml to use checkout@v4 and latest deploy @v4

• Update lint.yaml to use checkout@v4

• Update run-pre-commit-hooks.yaml to use checkout@v4

• Update test-coverage.yaml to use checkout@v4

• Re-build Rmarkdown files

---

• [ ] added unit tests and checked code coverage with covr::report() (should aim for 100%)
• [ ] ran devtools::document()
• [ ] ran lintr::lint_package() and resolved all lint warnings and notes
• [ ] ran styler::style_pkg() to make sure code matches the style guidelines
• [ ] ran R-CMD CHECK and resolved all issues

[francisbarton]

Thanks Tom!