Create reasonml merlin linter

copy @andreypopp 's ocaml merlin linter from this project into reason

ale_linters/reason/merlin.vim

@@ -0,0 +1,17 @@
+" Author: Andrey Popp -- @andreypopp
+" Description: Report errors in ReasonML code with Merlin
+
+if !exists('g:merlin')
+    finish
+endif
+
+function! ale_linters#reason#merlin#Handle(buffer, lines) abort
+    return merlin#ErrorLocList()
+endfunction
+
+call ale#linter#Define('reason', {
+\   'name': 'merlin',
+\   'executable': 'ocamlmerlin',
+\   'command': 'true',
+\   'callback': 'ale_linters#reason#merlin#Handle',
+\})