Fix for Input Numbers in Explanation Widgets

[SonicScrewdriver]

Summary:

This PR implements a quick bug fix for a p0 issue related to explanation widget, as it does not follow the typical PerseusRenderer format. I've also added some extra safety checks.

Test plan:

• Manual testing

[khan-actions-bot]

Gerald

Required Reviewers

• @Khan/perseus for changes to .changeset/curly-trains-smoke.md, packages/perseus/src/util/deprecated-widgets/input-number.ts

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[github-actions]

npm Snapshot: Published

Good news!! We've packaged up the latest commit from this PR (bd376eb) and published it to npm. You
can install it using the tag PR1900.

Example:

yarn add @khanacademy/perseus@PR1900

If you are working in Khan Academy's webapp, you can run:

./dev/tools/bump_perseus_version.sh -t PR1900

[Myranae]

Based on the talk in the huddle, this looks good to me. Good to go once the checks pass :) Love the safety measures :D Might be good to make sure this fixes the errors too ^_^

[github-actions]

Size Change: +108 B (+0.01%)

Total Size: 1.29 MB

Filename	Size	Change
packages/perseus/dist/es/index.js	425 kB	+108 B (+0.03%)

ℹ️ View Unchanged

Filename	Size
packages/kas/dist/es/index.js	39 kB
packages/keypad-context/dist/es/index.js	760 B
packages/kmath/dist/es/index.js	4.27 kB
packages/math-input/dist/es/index.js	77.9 kB
packages/math-input/dist/es/strings.js	1.79 kB
packages/perseus-core/dist/es/index.js	1.48 kB
packages/perseus-editor/dist/es/index.js	698 kB
packages/perseus-linter/dist/es/index.js	22.2 kB
packages/perseus/dist/es/strings.js	3.57 kB
packages/pure-markdown/dist/es/index.js	3.66 kB
packages/simple-markdown/dist/es/index.js	12.5 kB

_{compressed-size-action}

[jeremywiebe]

Could you attach a representative piece of data to this PR for posterity? I also don't really understand the issue based on the description. Even if you come back after the p0 event is over, I'd love to see this PR filled out a bit more for historical purposes.