fix: Do not split on Unicode characters with Line_Break=Glue property

[zmughal]

Specifically, this allows for using non-breaking space ("\u00A0", " ")
in text which is preserved when using SVG output.

Connects to:

• Multiple spaces are trimmed: Leading / trailing spaces are removed, mid-text spaces are converted into a single space #35,
• Markdown elements are broken up by word in SVG output ggtext#95.

---

Further test on SVG:

test_that("SVG preserves non-breaking spaces", {
  g <- textbox_grob(
    "S&nbsp;M&nbsp;E<br>B I A",
    width = unit(100, "pt"))

  # Create a temporary SVG file
  tmp_svg <- tempfile(fileext = ".svg")
  svglite::svglite(tmp_svg, width = 5, height = 5)
  grid.draw(g)
  dev.off()

  # Read SVG content
  svg_content <- readLines(tmp_svg)
  unlink(tmp_svg)  # cleanup

  text_elements <- svg_content[grep("^<text", svg_content)]
  text_inner <- text_elements |> purrr::map( ~ gsub('[^>]*>(.*</text>)$', '\\1', .x ) )

  expect_contains(text_inner,
                  c('S\u00A0M\u00A0E</text>',
                    'B</text>',
                    'I</text>',
                    'A</text>'))
})

[zmughal]

@bwiernik , seems that the action needs to be updated per https://github.com/wilkelab/gridtext/actions/runs/12111467778?

r-lib/actions/setup-r@v1 is deprecated. Please update your workflow to use the 'v2' version. Also look at the examples at https://github.com/r-lib/actions/tree/v2/examples because '@v2' workflows are much simpler than 'v1' workflows.