Add Rive

[abogawat]

Add the web-based Rive animation tool

Checklist

• [x] I made something good today 💐.
• [x] I put links in the correct format: [Tool](link) — description.
• [x] My description starts with the lower-case letter and ends with the full stop.
• [x] I put the tool in the alphabetical order.

Optional

• [x] I added the appropriate labels: free, open-source or mac.
• [x] I put the tool only to one category.
• [x] I followed Contribution Guidelines.

[itsnoa04]

Rive is a rebrand of flare which already exists. https://github.com/goabstract/Awesome-Design-Tools/pull/406 👆 this pull request modifies it

[abogawat]

@itsnoa04 Thanks! I didn't notice that. Closing my PR.