Unable to import TS file from Svelte file

[tomasbonco]

Describe the bug
The path of .ts dependency can't be resolved by .svelte file.

To Reproduce
Steps to reproduce the behavior:

1. Create a store.ts file, with content:

import { writable } from 'svelte/store'
export const something = writable( 10 )

2. In App.svelte add following line:

import {something} from './store'

And you'll get:

[!] Error: Could not resolve './store' from src\App.svelte
Error: Could not resolve './store' from src\App.svelte
    at error (d:\node\bug-repro\node_modules\rollup\dist\rollup.js:10162:30)
    at ModuleLoader.handleMissingImports (d:\node\bug-repro\node_modules\rollup\dist\rollup.js:17237:17)
    at ModuleLoader.<anonymous> (d:\node\bug-repro\node_modules\rollup\dist\rollup.js:17288:26)
    at Generator.next (<anonymous>)
    at fulfilled (d:\node\bug-repro\node_modules\rollup\dist\rollup.js:40:28)
    at <anonymous>

Expected behavior
Everything should be awesome, no errors reported.

Additional context
During filling of this bug I found out that import {something} from './store.ts' does work, but throws error into console:

src/App.svelte:4:27 - error TS2691: An import path cannot end with a '.ts' extension. Consider importing './store' instead.

[tomasbonco]

Even thou ignoring the error and using import .. from './store.ts' might look like a solution, there is an issue. Reference of store.ts imported in main.ts is different than the one imported inside App.svelte (each of them creates its own store). It makes the whole concept useless.

[pyoner]

@tomasbonco
The problem in rollup-plugin-typescript2 ezolenko/rollup-plugin-typescript2#172
To quick fix I recommend downgrading the rollup-plugin-typescript2 to version "0.21.0"