* Add Threads icon
Closes#8930
Threads is a new social media app by Instagram, made publicly available on July 5th, 2023. There appears to be no official brand guidelines page yet, so this SVG was pulled from the Wikipedia article for the app.
* add missing viewbox attribute
* fix: center path
* fix: run svgo against icon
* fix: actually center the icon
* Update _data/simple-icons.json
