Fix xaringan yaml documentation

README.md

 ``` yaml
 output:
   xaringan::moon_reader:
-    lib_dir: libs
     css: xaringan-themer.css
 ```
 
 ``` yaml
 output:
   xaringan::moon_reader:
-    lib_dir: libs
     css: ["xaringan-themer.css"]
     nature:
       highlightStyle: solarized-dark

man-roxygen/style-usage.R

 #' ```yaml
 #' output:
 #' xaringan::moon_reader:
-#'   css: xaringan-themer.css`
+#'   css: xaringan-themer.css
 #' ````
 #

man/fragments/_quick-intro.Rmd

 ```yaml
 output:
   xaringan::moon_reader:
-    lib_dir: libs
     css: xaringan-themer.css
 ```
 

man/fragments/_themes.Rmd

 ```yaml
 output:
   xaringan::moon_reader:
-    lib_dir: libs
     css: ["xaringan-themer.css"]
     nature:
       highlightStyle: solarized-dark

man/style_duo.Rd

 header. If you change the name of the output file using the \code{outfile}
 argument, use that name instead of the default file name.\if{html}{\out{<div class="yaml">}}\preformatted{output:
 xaringan::moon_reader:
-  css: xaringan-themer.css`
+  css: xaringan-themer.css
 }\if{html}{\out{</div>}}
 }
 

man/style_duo_accent.Rd

 header. If you change the name of the output file using the \code{outfile}
 argument, use that name instead of the default file name.\if{html}{\out{<div class="yaml">}}\preformatted{output:
 xaringan::moon_reader:
-  css: xaringan-themer.css`
+  css: xaringan-themer.css
 }\if{html}{\out{</div>}}
 }
 

man/style_duo_accent_inverse.Rd

 header. If you change the name of the output file using the \code{outfile}
 argument, use that name instead of the default file name.\if{html}{\out{<div class="yaml">}}\preformatted{output:
 xaringan::moon_reader:
-  css: xaringan-themer.css`
+  css: xaringan-themer.css
 }\if{html}{\out{</div>}}
 }
 

man/style_mono_accent.Rd

 header. If you change the name of the output file using the \code{outfile}
 argument, use that name instead of the default file name.\if{html}{\out{<div class="yaml">}}\preformatted{output:
 xaringan::moon_reader:
-  css: xaringan-themer.css`
+  css: xaringan-themer.css
 }\if{html}{\out{</div>}}
 }
 

man/style_mono_accent_inverse.Rd

 header. If you change the name of the output file using the \code{outfile}
 argument, use that name instead of the default file name.\if{html}{\out{<div class="yaml">}}\preformatted{output:
 xaringan::moon_reader:
-  css: xaringan-themer.css`
+  css: xaringan-themer.css
 }\if{html}{\out{</div>}}
 }
 

man/style_mono_dark.Rd

 header. If you change the name of the output file using the \code{outfile}
 argument, use that name instead of the default file name.\if{html}{\out{<div class="yaml">}}\preformatted{output:
 xaringan::moon_reader:
-  css: xaringan-themer.css`
+  css: xaringan-themer.css
 }\if{html}{\out{</div>}}
 }
 

man/style_mono_light.Rd

 header. If you change the name of the output file using the \code{outfile}
 argument, use that name instead of the default file name.\if{html}{\out{<div class="yaml">}}\preformatted{output:
 xaringan::moon_reader:
-  css: xaringan-themer.css`
+  css: xaringan-themer.css
 }\if{html}{\out{</div>}}
 }
 

man/style_solarized_dark.Rd

 header. If you change the name of the output file using the \code{outfile}
 argument, use that name instead of the default file name.\if{html}{\out{<div class="yaml">}}\preformatted{output:
 xaringan::moon_reader:
-  css: xaringan-themer.css`
+  css: xaringan-themer.css
 }\if{html}{\out{</div>}}
 }
 

man/style_solarized_light.Rd

 header. If you change the name of the output file using the \code{outfile}
 argument, use that name instead of the default file name.\if{html}{\out{<div class="yaml">}}\preformatted{output:
 xaringan::moon_reader:
-  css: xaringan-themer.css`
+  css: xaringan-themer.css
 }\if{html}{\out{</div>}}
 }
 

man/style_xaringan.Rd

 header. If you change the name of the output file using the \code{outfile}
 argument, use that name instead of the default file name.\if{html}{\out{<div class="yaml">}}\preformatted{output:
 xaringan::moon_reader:
-  css: xaringan-themer.css`
+  css: xaringan-themer.css
 }\if{html}{\out{</div>}}
 }