refacto: move toggle help and filter toggles into actions

also fix explorer to properly remove element on update when filter is
applied

lua/nvim-tree/actions/toggle-help.lua

@@ -0,0 +1,8 @@
+local M = {}
+
+function M.fn()
+  require"nvim-tree.view".toggle_help()
+  return require"nvim-tree.lib".redraw()
+end
+
+return M