fix(types): add null to selectedItem type (#1642)

fix(hooks): suppressRefError improvement (#1618)

fix(useMouseAndTouchTrackers): dependency array (#1612)

* fix(useMouseAndTouchTrackers): dependency array

* remove console logs

* some improvements

* pass references

fix(hooks): return boolean for aria-selected (#1603)

fix(highlightedIndex): do not highlight disabled items (#1601)

fix(types): replace index with number (#1592)

fix(hooks): fix highlight on arrow key opening (#1591)

* fix(hooks): fix highlight on arrow key opening

* remove redundant tests

fix(hooks): do not highlight disabled items on menu open (#1587)

fix(a11yStatus): pass correct dependency array (#1586)

feat: V9 (#1582)

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<!-- What changes are being made? (What feature/bug is being fixed here?) -->

**What**:
BREAKING CHANGE: Release Downshift v9.

<!-- Why are these changes necessary? -->

**Why**:
Release the changes in:
- #1580
- #1579
- #1583

Closes #1322.
Closes #1244.
Closes #1227
Closes #1225.
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**How**:
Merged the PRs in this branch.
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**Checklist**:

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- [x] Documentation
- [x] Tests
- [x] TypeScript Types
- [ ] Flow Types
- [x] Ready to be merged
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