Migrate lakeFS webui to TypeScript

[eladlachmi]

Migrate the lakeFS webui to TypeScript. This effort will include setting up the npm project for using TypeScript and migrating existing code to TS, so we don't need to start off with a lax tsconfig, which will require additional refactoring efforts in the future.

As the code base grows, TS's value will hugely outweigh its overhead. It will also make it easier to contribute to the webui of lakeFS confidently.

Feedback is very welcome!