new icon: istio (original, original-wordmark)

[bkanishka004]

Double check these details before you open a PR

• PR does not match another non-stale PR currently opened
• PR name matches the format
• PR's base is the develop branch.
• Your icons are inside a folder as seen here
• SVG matches the standards laid out here
• A new object is added in the devicon.json file at the correct alphabetic position as seen here

**This PR closes #2499 **

Link to prove your SVG is correct and up-to-date.

https://istio.io/

[github-actions]

Hi!

I'm the check-bot and we have some issues with your PR:

devicon.json is not sorted correctly.
Please make sure that your icon is added in the `devicon.json` file at the correct alphabetic position
as seen here: https://github.com/devicons/devicon/wiki/Updating-%60devicon.json%60

Check our CONTRIBUTING guide for more details regarding these errors.

Please address these issues. When you update this PR, I will check your SVGs again.

Thanks for your help,
SVG-Checker Bot 😄