Fix typo with background_size_fallback

.Rbuildignore

@@ -8,3 +8,4 @@
 ^_.+$
 ^docs$
 ^index\.Rmd$
+^man-roxygen$

R/write_theme.R

@@ -167,7 +167,7 @@ write_xaringan_theme <- function(
   
   # prepare variables for template
   body_font_family <- paste(c(text_font_family, text_font_family_fallback, text_font_base), collapse = ', ')
-  backround_size_fallback <- if (is.null(background_position)) "cover" else "100%"
+  background_size_fallback <- if (is.null(background_position)) "cover" else "100%"
   background_size <- background_image %??% (background_size %||% background_size_fallback)
   title_slide_background_size <- title_slide_background_size %||% (
     title_slide_background_image %??% "cover"

inst/scripts/write_xaringan_theme_body.R

@@ -41,7 +41,7 @@ for (var in f_args) {
 
 # prepare variables for template
 body_font_family <- paste(c(text_font_family, text_font_family_fallback, text_font_base), collapse = ', ')
-backround_size_fallback <- if (is.null(background_position)) "cover" else "100%"
+background_size_fallback <- if (is.null(background_position)) "cover" else "100%"
 background_size <- background_image %??% (background_size %||% background_size_fallback)
 title_slide_background_size <- title_slide_background_size %||% (
   title_slide_background_image %??% "cover"