Multiple hotkeys for headings

[dylans]

Issue

When specifying options for headings, only 1 hotkey would get handled (refs #518)

What I did

• Added support for multiple hotkey handlers by treating the key passed in as a string or array
• Updated stories invoking the heading plugin to add hotkeys for h1, h2, and h3

Checklist

• The new code matches the existing patterns and styles.
• The stories still work (run yarn storybook).
• The stories are updated when relevant: stories for plugins, knobs for options.

[codecov]

Codecov Report

Merging #539 (21c7cd4) into next (fcc04f8) will decrease coverage by 0.31%.
The diff coverage is 50.00%.

@@            Coverage Diff             @@
##             next     #539      +/-   ##
==========================================
- Coverage   76.93%   76.61%   -0.32%     
==========================================
  Files         339      339              
  Lines        4063     4076      +13     
  Branches      871      875       +4     
==========================================
- Hits         3126     3123       -3     
- Misses        933      949      +16     
  Partials        4        4              

Impacted Files	Coverage Δ
...late-plugins/src/elements/heading/HeadingPlugin.ts	100.00% <ø> (ø)
...c/common/utils/getOnHotkeyToggleNodeTypeDefault.ts	70.00% <50.00%> (-30.00%)	⬇️
...gins/src/common/utils/getOnHotkeyToggleNodeType.ts	30.76% <0.00%> (-30.77%)	⬇️
...es/slate-plugins/src/common/queries/queryEditor.ts	0.00% <0.00%> (ø)
...late-plugins/src/dnd/hooks/useDropBlockOnEditor.ts	27.50% <0.00%> (ø)

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update fcc04f8...21c7cd4. Read the comment docs.

[zbeyens]

Can you set these options in options so we don't have to duplicate in all stories?

[dylans]

Let me know if this update is what you had in mind, thanks!

[zbeyens]

LGTM, thanks!