Increment version number to 0.4.3.9000

DESCRIPTION

@@ -1,7 +1,7 @@
 Type: Package
 Package: xaringanthemer
 Title: Custom 'xaringan' CSS Themes
-Version: 0.4.3
+Version: 0.4.3.9000
 Authors@R: 
     person("Garrick", "Aden-Buie", , "garrick@adenbuie.com", role = c("aut", "cre"),
            comment = c(ORCID = "0000-0002-7111-0077"))

NEWS.md

@@ -1,3 +1,5 @@
+# xaringanthemer (development version)
+
 # xaringanthemer 0.4.3
 
 - Update the spelling of `colour` for compatibility with ggplot2 >= 3.5.1 (@teunbrand #79).