Linter Rule: Warn when `if` is being used with `<%=`

### Good

```erb
<% if condition? %>
  ...
<% elsif another_condition? %>
  ...
<% end %>
```

### Bad

```erb
<%= if condition? %>
  ...
<% elsif another_condition? %>
  ...
<% end %>
```


```erb
<% if condition? %>
  ...
<%= elsif another_condition? %>
  ...
<% end %>
```

I think this should also apply for another other control flow, like when/case, for, while, until, unless, etc.
