Unicode support for filenames

[vilarfg]

Describe the bug
Filenames with Unicode characters on them produce errors.

Stacktraces

ERROR in ./src/routes/简体中文/index.svelte
Module build failed (from ./node_modules/svelte-loader/index.js):
Error: Error: Error: Could not derive component name from file /{my-repo_name}/src/routes/简体中文/index.svelte

Information about your Svelte project:

• Svelte 3.12.1, Webpack

To Reproduce
Simply name a file something like 中国.svelte and watch it fail 😭

Expected behavior
For this to work 😉 .

Severity
I REALLY need this! So I worked out a fix and a pull request is coming your way shortly 🎉