Bump react-simplemde-editor from v4.1.5 to v5.2.0

[myarmolinsky]

Bump react-simplemde-editor from v4.1.5 to v5.2.0

Patches vulnerability caused by having marked <= v4.0.9
Also adds easymde as a dependency to keep the MarkdownEditor defaultStyle

Change-type: patch

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Contributor checklist

• I have regenerated jest snapshots for any affected components with npm run generate-snapshots

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