I am not super familiar with typescript but you either need to see if there is a @types/rake-js npm module, or you need to create your own rake-js.d.ts module declaration. But typescript is not required if you feel more comfortable in vanilla JS. You can remove the typescript plugins for rollup, and do some renaming of files and develop your plugin without it. If you use VS Code it can still show you the obsidian type declarations on command click, and will still give you decent type ahead support.
The only hard rule is that your `main.js bundle contain all the code required to run your plugin, how you get there is up to you.