add air toml

Author: strengejacke

.Rbuildignore

@@ -26,3 +26,5 @@
 \.code-workspace$
 \.lintr$
 ^CRAN-SUBMISSION$
+^[.]?air[.]toml$
+^\.vscode$

air.toml

@@ -0,0 +1,8 @@
+[format]
+line-width = 90
+indent-width = 2
+indent-style = "space"
+line-ending = "auto"
+persistent-line-breaks = true
+exclude = []
+default-exclude = true