Add MenuItem disabled prop

[silviuaavram]

Feature Request

As a result of #83 , it is required for the MenuItem Component to handle the disabled prop and act accordingly.

Problem description

The disabled prop has been added to MenuItem, in order to be used to add the aria-disabled attribute on the element. However, adding this prop should trigger the actual disabled behaviour for the menu item, similar to how Button behaves, for instance.

Proposed solution

Provide functionality to the MenuItem component in order to make it act similarly to Button when it receives the disabled=true

[silviuaavram]

@kuzhelov should we close this one? the PR was merged and the MenuItem has been given the disabled handled prop.

[levithomason]

Yes, please close issues when PRs are merged. Do this automatically by adding Fixes #186 in plain text to the PR description.

[miroslavstastny]

This issue was created as a follow-up of #83. In that PR, disabled prop was added to MenuItem but no support for disabled menu item was implemented.