Ignore more build files and sort .Rbuildignore

Sort the `.Rbuildignore` file using the C locale to get some semblance
of consistency. Maybe not the best ordering, but trivial to reproduce,
and thus to keep consistent.

.Rbuildignore

@@ -1,19 +1,21 @@
-^\.lintr$
-^\.Rprofile$
-^\.gitignore$
+^.*\.Rproj$
+^LICENSE.md$
 ^Makefile$
+^Meta$
 ^README\.md$
 ^README\.rmd$
-^LICENSE.md$
-^pkgdown$
+^\.Rprofile$
+^\.Rproj\.user$
+^\.clangd$
+^\.github$
+^\.gitignore$
+^\.lintr$
 ^cran$
 ^doc$
 ^docs$
 ^figures$
-^.*\.Rproj$
-^\.Rproj\.user$
-^Meta$
+^pkgdown$
 ^renv$
 ^renv\.lock$
-^\.github$
 ^scripts$
+^tmp$