Add Sticky component

[alexander-schranz]

Q	A
Bug fix?	no
New feature?	yes
BC breaks?	no
Deprecations?	no
Fixed tickets	fixes #
Related issues/PRs	#6676, #6669
License	MIT
Documentation PR	sulu/sulu-docs#

What's in this PR?

Add a sticky component which childs allow to behave different between stick state.

Why?

This will be required for the BlockToolbar.

Example Usage

<Sticky>{
    (isSticky) => <span>{isSticky ? 'Stick' : 'Unsticky'}</span>
}</Sticky>

To Do

• Create a documentation PR

[alexander-schranz]

Else position relative elements are above the sticky toolbar:

https://jsfiddle.net/oey4dq1x/

[niklasnatter]

😱

[niklasnatter]

this will probably push the sticky element above our overlays/dialogs too 😕 i think we can prevent that from happening by setting z-index: 0 in the parent component that uses this component, right?

[niklasnatter]

unfortunately, i think there is no way around this problem while keeping the needed functionality, so i am going to merge this 🙂