Add support for erlfmt fixer (#3602)

* Add support for `erlfmt`

* Add missing entry to table of contents

* Fix warnings

* Add missing tools to supported tools

autoload/ale/fixers/erlfmt.vim

@@ -0,0 +1,21 @@
+" Author: AntoineGagne - https://github.com/AntoineGagne
+" Description: Integration of erlfmt with ALE.
+
+call ale#Set('erlang_erlfmt_executable', 'erlfmt')
+call ale#Set('erlang_erlfmt_use_global', get(g:, 'ale_use_global_executables', 0))
+call ale#Set('erlang_erlfmt_options', '')
+
+function! ale#fixers#erlfmt#GetExecutable(buffer) abort
+    return ale#node#FindExecutable(a:buffer, 'erlang_erlfmt', ['erlfmt'])
+endfunction
+
+function! ale#fixers#erlfmt#Fix(buffer) abort
+    let l:options = ale#Var(a:buffer, 'erlang_erlfmt_options')
+    let l:executable = ale#fixers#erlfmt#GetExecutable(a:buffer)
+
+    let l:command = ale#Escape(l:executable) . (empty(l:options) ? '' : ' ' . l:options) . ' %s'
+
+    return {
+    \   'command': l:command
+    \}
+endfunction