docs: fold in Copilot's #115 review nits + restore lost VignetteIndexEntry (#116)

#115 was merged from commit 437c48a, before the 2dcdc73 force-push that
fixed the vignette index entry, so that fix was lost; this restores it.
Plus the three Copilot inline comments on #115:

- `vignettes/dockerfiler.Rmd`: section heading "Create a Dockerfile
  from an renv.lock" -> "... from a renv.lock" (article).
- `R/rthis.R` `@examples`, `vignettes/dockerfiler.Rmd` "Basic
  workflow" chunk, `README.Rmd`: the illustrative
  `install.packages(..., repos = "http://cran.irsn.fr/")` now uses
  the canonical HTTPS CRAN mirror `https://cloud.r-project.org`
  instead of a plaintext-HTTP regional mirror.
- restored `%\VignetteIndexEntry{Getting started with dockerfiler}`
  so it matches the vignette's YAML `title:` (silences the
  rmarkdown title-mismatch warning).

regenerated `man/r.Rd`; re-knit `README.md`. No code-logic change.
`devtools::test()` on the touched test file: 0 failures. Vignette
renders clean. No en/em-dashes in source.

Author: VincentGuyader

R/rthis.R

@@ -12,7 +12,7 @@
 #'
 #' @examples
 #' r(print("yeay"))
-#' r(install.packages("plumber", repos = "http://cran.irsn.fr/"))
+#' r(install.packages("plumber", repos = "https://cloud.r-project.org"))
 r <- function(code) {
   code <- paste(trimws(deparse(substitute(code))), collapse = " ")
   glue("R -e {shQuote(code, type = 'sh')}")

README.Rmd

@@ -73,7 +73,7 @@ my_dock$COMMENT("Install required R package.")
 Wrap your raw R Code inside the `r()` function to turn it into a bash command with `R -e`.
 
 ```{r}
-my_dock$RUN(r(install.packages("attempt", repos = "http://cran.irsn.fr/")))
+my_dock$RUN(r(install.packages("attempt", repos = "https://cloud.r-project.org")))
 ```
 
 Classical Docker stuffs:

README.md

@@ -64,7 +64,7 @@ Wrap your raw R Code inside the `r()` function to turn it into a bash
 command with `R -e`.
 
 ``` r
-my_dock$RUN(r(install.packages("attempt", repos = "http://cran.irsn.fr/")))
+my_dock$RUN(r(install.packages("attempt", repos = "https://cloud.r-project.org")))
 ```
 
 Classical Docker stuffs:

man/r.Rd

@@ -4,7 +4,7 @@ author: "Colin Fay"
 date: "`r Sys.Date()`"
 output: rmarkdown::html_vignette
 vignette: >
-  %\VignetteIndexEntry{getting_started}
+  %\VignetteIndexEntry{Getting started with dockerfiler}
   %\VignetteEngine{knitr::rmarkdown}
   %\VignetteEncoding{UTF-8}
 ---
@@ -53,7 +53,7 @@ my_dock$MAINTAINER("Colin FAY", "contact@colinfay.me")
 Wrap your raw R Code inside the `r()` function to turn it into a bash command with `R -e`.
 
 ```{r}
-my_dock$RUN(r(install.packages("attempt", repos = "http://cran.irsn.fr/")))
+my_dock$RUN(r(install.packages("attempt", repos = "https://cloud.r-project.org")))
 ```
 
 Classical Docker stuffs:
@@ -131,7 +131,7 @@ pulls Linux binaries from Posit Public Package Manager
 (`https://p3m.dev/cran/latest`). Pass `FROM = "rocker/r-base"` or
 `repos = c(CRAN = "https://cran.rstudio.com/")` to opt out.
 
-## Create a Dockerfile from an renv.lock
+## Create a Dockerfile from a renv.lock
 
 If your project uses `{renv}`, `dock_from_renv()` turns the `renv.lock`
 into a Dockerfile that restores the exact pinned versions.