Fix code-language-switch a11y lighthouse audit

[AndrewJakubowicz]

Context

The code language switch was triggering the following audit issue: https://dequeuniversity.com/rules/axe/4.7/label-content-name-mismatch

Basically it wanted the aria-label to contain JS TS within it. This didn't make much sense to me, so I looked up the switch accessibility pattern https://www.w3.org/WAI/ARIA/apg/patterns/switch/

Fix

Use the same accessibility pattern as https://www.w3.org/WAI/ARIA/apg/patterns/switch/examples/switch-button/ and hide the inner text content. This prevents redundant announcement of state by screen readers.

We can hide the JS and TS text from the accessibility tree as our switch already provides full information via aria-label, and aria-checked. This then passes the audit because we no longer need to include the string JS TS in the aria label.

Testing

Tested by looking at the accessibility tree developer console. The switch has the label Toggle TypeScript, and checked state of true or false.

Lighthouse audit is now passing for this component.

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