1. User can specify a hash `context[:img_attrs]` to change the `img` tag
attributes, e.g. `{ "draggable" => false }`

2. The hash key can be either `String` / `Symbol` (indifferent access)

  `{ "draggable" => false }` / `{ draggable: false }`

  =>

  `<img draggable="false">`

3. The hash value can be either anything / proc-like object

  Proc-like object with default argument `name`:

  Given name is `:shipit:`

  `{ title: ->(name) { |n| n.gsub(":", "") } }`

  =>

  `<img title="shipit">`

  So you can do any customisations with the attribute.

4. The hash value nil means clear the attribute of img tag

  For example, to clear the default `height`, `width`, and `align`
  attributes, pass `{ height: nil, width: nil, align: nil }` to
  `context[:img_attrs]`.

5. Refine tests with consistent styles