[l10n] Add Icelandic (is-IS) locale

[magnimarels]

Added Icelandic translation for the x-data-grid

• I have followed (at least) the PR section of the contributing guide.

[mui-bot]

Localization writing tips ✍️

Seems you are updating localization 🌍 files.

Thank you for contributing to the localization! 🎉 To make your PR perfect, here is a list of elements to check: ✔️

• Verify if the PR title respects the release format. Here are two examples (depending if you update or add a locale file)

  [l10n] Improve Swedish (sv-SE) locale
  [l10n] Add Danish (da-DK) locale

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[github-actions]

This pull request has conflicts, please resolve those before we can evaluate the pull request.

[LukasTy]

Thank you for your contribution! 🙏
Could you please sync (merge into) your branch with the latest upstream/master to avoid unwanted changes in the PR? 🤔

[LukasTy]

🔔 Gentle ping @mui/xgrid.

[MBilalShafi]

Thank you for your contribution 👍

[LukasTy]

Forcing a merge as the e2e website seems to be flaky and would definitely pass. 👌