feat(LEMS-1733): adds aria labels to line segment

[anakaren-rojas]

Summary:

• Adds aria label and description to whole line segment
• Adds aria label for individual end points of line segment

Issue: LEMS-1733

Test plan:

1. Navigate to Chromatic
2. Select Line Segment Interactive Graph from drop down
3. Validate screen reader can read line segment

Expected behavior

1. Screen reader reads aria label for whole graph: A line segment on a coordinate plane
2. Screen reader reads aria description for whole graph: Endpoint 1 at ${point1X} comma ${point1Y}. Endpoint 2 ${point2X} comma ${point2Y}. Segment length %(length)s
3. When selected, screen reader reads aria label for end points: Endpoint ${endpointNumber} at ${x} comma ${y}
4. When moving a point, aria labels adjust to include new end points and length, as appropriate

Screenshots:

[github-actions]

npm Snapshot: Published

Good news!! We've packaged up the latest commit from this PR (06114d8) and published it to npm. You
can install it using the tag PR2032.

Example:

yarn add @khanacademy/perseus@PR2032

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

./dev/tools/bump_perseus_version.sh -t PR2032

[github-actions]

Size Change: +728 B (+0.06%)

Total Size: 1.27 MB

Filename	Size	Change
packages/perseus/dist/es/index.js	418 kB	+447 B (+0.11%)
packages/perseus/dist/es/strings.js	5.21 kB	+281 B (+5.7%)	🔍

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	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	688 kB
packages/perseus-linter/dist/es/index.js	22.2 kB
packages/pure-markdown/dist/es/index.js	3.67 kB
packages/simple-markdown/dist/es/index.js	12.5 kB

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[nishasy]

A couple of small requests.