feat: Add project option file support for astyle

autoload/ale/fixers/astyle.vim

@@ -4,6 +4,7 @@
 function! s:set_variables() abort
     for l:ft in ['c', 'cpp']
         call ale#Set(l:ft . '_astyle_executable', 'astyle')
+        call ale#Set(l:ft . '_astyle_options', '')
     endfor
 endfunction
 
@@ -19,9 +20,11 @@ endfunction
 function! ale#fixers#astyle#Fix(buffer) abort
     let l:executable = ale#fixers#astyle#Var(a:buffer, 'executable')
     let l:filename = ale#Escape(bufname(a:buffer))
+    let l:options = ale#fixers#astyle#Var(a:buffer, 'options')
     let l:command = ' --stdin=' . l:filename
 
     return {
     \   'command': ale#Escape(l:executable) . l:command
+    \     . (empty(l:options) ? '' : ' --project=' . l:options)
     \}
 endfunction