[l10n] Add Norwegian Nynorsk (nn-NO) locale

[AnderzL7]

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

• Adds norwegian nynorsk (nnNO) locale to x-date-pickers

[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

• Update the documentation of supported locales by running pnpm l10n
• Verify that you have added an export line in src/locales/index.ts for the new locale.
• Run pnpm docs:api which should add your new translation to the list of exported interfaces.
• Clean files with pnpm prettier.

Deploy preview: https://deploy-preview-13946--material-ui-x.netlify.app/

Generated by 🚫 dangerJS against 2c871a8

[AnderzL7]

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

• Update the documentation of supported locales by running pnpm l10n
• Verify that you have added an export line in src/locales/index.ts for the new locale.
• Run pnpm docs:api which should add your new translation to the list of exported interfaces.
• Clean files with pnpm prettier.

Deploy preview: https://deploy-preview-13588--material-ui-x.netlify.app/

Generated by 🚫 dangerJS against 1790b1a

• Verify if the PR title respects the release format.
• Update the documentation of supported locales by running pnpm l10n
• Verify that you have added an export line in src/locales/index.ts for the new locale.
• Run pnpm docs:api which should add your new translation to the list of exported interfaces.
• Clean files with pnpm prettier.

[LukasTy]

Thank you for your continued contribution! 🙏