Add ALEFixPre and ALEFixPost events

To run autocmd before and after every fix cycle.

Fixes #623 (`ALELintPre` was added in #1203).

autoload/ale/fix.vim

@@ -54,6 +54,8 @@ function! ale#fix#ApplyQueuedFixes() abort
         let l:should_lint = l:data.changes_made
     endif
 
+    silent doautocmd <nomodeline> User ALEFixPost
+
     " If ALE linting is enabled, check for problems with the file again after
     " fixing problems.
     if g:ale_enabled
@@ -463,6 +465,8 @@ function! ale#fix#Fix(...) abort
     call ale#fix#RemoveManagedFiles(l:buffer)
     call ale#fix#InitBufferData(l:buffer, l:fixing_flag)
 
+    silent doautocmd <nomodeline> User ALEFixPre
+
     call s:RunFixer({
     \   'buffer': l:buffer,
     \   'input': g:ale_fix_buffer_data[l:buffer].lines_before,