Organize the project folders

[hermet]

In thorvg.web, we may plan to have multiple projects in single repo here. It'd be better to separate each projects on different dir.

root
- thorvg(submodule)/
- perf-test/
- lottie-player/
- thorvg-js/

Currently, perf-test is on separated dir and lottie-player is on just root. Now it doesn't seem to be issue because perf-test will be moved soon. I believe we can have good directory structures later likely mono repo! :)

Originally posted by @tinyjin in #13 (comment)