feat: Add cpp support to astyle fixer

autoload/ale/fixers/astyle.vim

@@ -1,14 +1,27 @@
 " Author: James Kim <jhlink@users.noreply.github.com>
-" Description: Fix C files with astyle.
+" Description: Fix C/C++ files with astyle.
 
-call ale#Set('c_astyle_executable', 'astyle')
+function! s:set_variables() abort
+    for l:ft in ['c', 'cpp']
+        call ale#Set(l:ft . '_astyle_executable', 'astyle')
+    endfor
+endfunction
+
+call s:set_variables()
+
+function! ale#fixers#astyle#Var(buffer, name) abort
+    let l:ft = getbufvar(str2nr(a:buffer), '&filetype')
+    let l:ft = l:ft =~# 'cpp' ? 'cpp' : 'c'
+
+    return ale#Var(a:buffer, l:ft . '_astyle_' . a:name)
+endfunction
 
 function! ale#fixers#astyle#Fix(buffer) abort
-    let l:executable = ale#Var(a:buffer, 'c_astyle_executable')
+    let l:executable = ale#fixers#astyle#Var(a:buffer, 'executable')
+    let l:command = ' %t'
 
     return {
-    \   'command': ale#Escape(l:executable)
+    \   'command': ale#Escape(l:executable) . l:command,
-    \       . ' %t',
     \   'read_temporary_file': 1,
     \}
 endfunction