Add support for qmlfmt fixer (#1651)

* Add support for qmlfmt fixer

autoload/ale/fixers/qmlfmt.vim

@@ -0,0 +1,11 @@
+call ale#Set('qml_qmlfmt_executable', 'qmlfmt')
+
+function! ale#fixers#qmlfmt#GetExecutable(buffer) abort
+    return ale#Var(a:buffer, 'qml_qmlfmt_executable')
+endfunction
+
+function! ale#fixers#qmlfmt#Fix(buffer) abort
+     return {
+     \  'command': ale#Escape(ale#fixers#qmlfmt#GetExecutable(a:buffer)),
+     \}
+endfunction