Add deadnix linter (#4443)

autoload/ale/handlers/deadnix.vim

@@ -0,0 +1,33 @@
+function! ale#handlers#deadnix#Handle(buffer, lines) abort
+    let l:output = []
+
+    for l:line in a:lines
+        try
+            let l:file = ale#util#FuzzyJSONDecode(l:line, v:null)
+        catch
+            continue
+        endtry
+
+        if type(l:file) isnot v:t_dict
+            continue
+        endif
+
+        for l:error in l:file['results']
+            try
+                let l:ale_error = {
+                \   'lnum': l:error['line'],
+                \   'col': l:error['column'],
+                \   'end_col': l:error['endColumn'],
+                \   'text': l:error['message'],
+                \   'type': 'W',
+                \}
+            catch
+                continue
+            endtry
+
+            call add(l:output, l:ale_error)
+        endfor
+    endfor
+
+    return l:output
+endfunction