feat(a11y): add default children behavior to behaviors

[silviuaavram]

Fixes #1008

It adds child behaviors by default to Menu related behaviors:

• menuBehavior/submenuBehavior - menuItemBehavior
• tabListBehavior - tabBehavior
• toolbarBehavior - toolbarButtonBehavior

[sophieH29]

I would name it childBehavior as it is only one.

[layershifter]

But, why it should be single? We also have MenuDivider that can be iterated in the same scope...

[sophieH29]

I the sense of AccessibilityBehavior type, it can have only one child behavior. For e.g.

MenuBehavior= (props) => {
...
childBehavior: menuItemBehavior
}

[layershifter]

It's not true. menuBehavior has multiple siblings: menuItemBehavior, menuDividerBehavior & submenuBehavior. I had an offline conversation with @miroslavstastny and we agreed on the same thing that was proposed originally:

menuBehavior= (props) => {
  // ...
  childBehaviors: {
     item: menuItemBehavior,
     divider: menuDividerBehavior,
  }
}

It allows to override behaviors for all child items and it's aligned with existing structure on attributes and keyHandlers. Please take one more look on this change.

[codecov]

Codecov Report

Merging #1282 into master will decrease coverage by 0.04%.
The diff coverage is 50%.

@@            Coverage Diff             @@
##           master    #1282      +/-   ##
==========================================
- Coverage   72.77%   72.73%   -0.05%     
==========================================
  Files         736      736              
  Lines        5627     5633       +6     
  Branches     1624     1630       +6     
==========================================
+ Hits         4095     4097       +2     
- Misses       1527     1529       +2     
- Partials        5        7       +2

Impacted Files	Coverage Δ
...lib/accessibility/Behaviors/Tab/tabListBehavior.ts	100% <ø> (ø)	⬆️
...ib/accessibility/Behaviors/Menu/submenuBehavior.ts	100% <ø> (ø)	⬆️
...accessibility/Behaviors/Toolbar/toolbarBehavior.ts	100% <ø> (ø)	⬆️
...c/lib/accessibility/Behaviors/Menu/menuBehavior.ts	100% <ø> (ø)	⬆️
packages/react/src/components/Menu/Menu.tsx	68.57% <50%> (-7.3%)	⬇️

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[jurokapsiar]

childBehaviors is optional, check its existence before accessing divider

[jurokapsiar]

childBehaviors is optional, check its existence before accessing item