docs:(attrs) extended @element ngDisabled

[Mephiztopheles]

Using Intellij's IDE will cause this not to mark ng-disabled on buttons or selects as not allowed attribute

What kind of change does this PR introduce? (Bug fix, feature, docs update, ...)
docs update

What is the current behavior? (You can also link to an open issue here)
Intellij will mark ng-disabled as not allowed attribute on some form elements

What is the new behavior (if this is a feature change)?
ng-disabled is now also allowed on buttons and selects

Does this PR introduce a breaking change?
nope

Please check if the PR fulfills these requirements

• The commit message follows our guidelines
• Fix/Feature: Docs have been added/updated
• Fix/Feature: Tests have been added; existing tests pass

Other information:
none

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[Mephiztopheles]

I signed it!

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CLAs look good, thanks!

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CLAs look good, thanks!

[gkalpak]

Theoretically, it can go on any element, but I guess it makes sense to only recommend it for form controls.
What about textarea?

[Mephiztopheles]

u're right, there might be some elements missing. At this moment it is just input and i kinda hatet, my idea shows me some errors, so i just added what i need. Due to the build fail, I don't think, that i will improve this pull request, or make any other request. So IF you want to improve the documentation, you could just add the form elements to the element tag and i will be pleased

[Narretz]

You can still add textarea in a new commit, the build failures are unrelated to your changes