[Locked Figure Aria] Implement locked line aria label behavior on graph

[nishasy]

Summary:

• Add ariaLabel field to LockedLineType
• Add the aria label behavior to the LockedLine on the mafs graph

Issue: https://khanacademy.atlassian.net/browse/LEMS-2376

Test plan:

yarn jest packages/perseus/src/widgets/interactive-graphs/interactive-graph.test.tsx

Storybook

• Go to http://localhost:6006/iframe.html?args=&id=perseuseditor-widgets-interactive-graph--mafs-with-locked-figure-labels-all-flags&viewMode=story
• Use a screen reader to navigate through the preview graph
• Using the screenreader controls (VO + arrow keys) should be able to navigate to
  the locked line. It should read out as "Point PQ".

locked-line-aria-experience.mov

[github-actions]

npm Snapshot: Published

Good news!! We've packaged up the latest commit from this PR (025d281) and published it to npm. You
can install it using the tag PR1683.

Example:

yarn add @khanacademy/perseus@PR1683

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

./dev/tools/bump_perseus_version.sh -t PR1683

[github-actions]

Size Change: +29 B (0%)

Total Size: 864 kB

Filename	Size	Change
packages/perseus/dist/es/index.js	418 kB	+29 B (+0.01%)

ℹ️ View Unchanged

Filename	Size
packages/kas/dist/es/index.js	38.3 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	78 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	280 kB
packages/perseus-linter/dist/es/index.js	22.2 kB
packages/perseus/dist/es/strings.js	3.4 kB
packages/pure-markdown/dist/es/index.js	3.66 kB
packages/simple-markdown/dist/es/index.js	12.4 kB

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[khan-actions-bot]

Gerald

Required Reviewers

• @Khan/perseus for changes to .changeset/fresh-sheep-invent.md, packages/perseus/src/perseus-types.ts, packages/perseus/src/widgets/interactive-graphs/graph-locked-layer.tsx, packages/perseus/src/widgets/interactive-graphs/interactive-graph-question-builder.test.ts, packages/perseus/src/widgets/interactive-graphs/interactive-graph-question-builder.ts, packages/perseus/src/widgets/interactive-graphs/interactive-graph.test.tsx, packages/perseus/src/widgets/interactive-graphs/interactive-graph.testdata.ts, packages/perseus/src/widgets/interactive-graphs/locked-figures/locked-line.tsx

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[benchristel]

LGTM!