Replace b:filetype with filetype (#216)

b:filetype is an invalid variable name

Fix #215

Author: xuhdev

plugin/editorconfig.vim

@@ -384,7 +384,7 @@ function! s:ApplyConfig(config) abort " Set the buffer options {{{1
     endif
 
     " Do not process netrw buffers
-    if &b:filetype == 'netrw'
+    if &filetype == 'netrw'
         return
     endif