Add a variant to Text block to support highlight text area

[JiangLong2019]

Please always provide the GitHub issue(s) your PR is for, as well as test URLs where your change can be observed (before and after):

Fixes #140

Test URLs:

• Original: https://www.sunstar-foundation.org/en/awards/world-hygienist/how-to-apply

• Before: https://main--sunstar-foundation--hlxsites.hlx.live/en/awards/world-hygienist/how-to-apply

• After: https://text-highlight--sunstar-foundation--hlxsites.hlx.live/en/awards/world-hygienist/how-to-apply

• [x] New variations introduced in this PR

Variation Name	Documentation
Text(highlight)

[aem-code-sync[bot]]

Hello, I'm the AEM Code Sync Bot and I will run some actions to deploy your branch and validate page speed. In case there are problems, just click a checkbox below to rerun the respective action.

• [ ] Re-run PSI checks
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Commits

* [439f049](https://github.com/hlxsites/sunstar-foundation/pull/141/commits/439f04911ea512845569cb66b3c5b8d1f5c929d3) :white_check_mark: (latest) * [52ce3eb](https://github.com/hlxsites/sunstar-foundation/pull/141/commits/52ce3eb665da3bff0f1492df0053c37fe4ddbe54) :white_check_mark:

[aem-code-sync[bot]]

Page	Scores	Audits	Google
/en/awards/world-hygienist/how-to-apply

[github-actions[bot]]

:small_orange_diamond: 1 visual difference detected

• /sidekick/blocks/tables (main vs branch)
  276836 pixels (ratio 0.05 of all image pixels) are different.

The diff images are attached in the artifact