vscodeIgnore some unused files to optimize extension size

[jasonlyu123]

#139

• Ignore some different purpose builds for typescript. We didn't use them.
• Ignore typescript localization. We didn't enable localized diagnostic.
• Ignore large ESM files, We're currently using common js

Tested and it brings the size down from 105MB to 42MB. With this file size reduction, it might make sense to ship some commonly used preprocess libraries to improve UX.
About typescript localization, it's possible to enable this. So if we want to enable it in the future, I think we can keep these files.

To test packaging this, run these commands:

rm package.json yarn.lock
cd packages/svelte-vscode
yarn install
vsce package

And install the vsix file or unzip it to see the folder structure.

[dummdidumm]

This is great, thank you! If we want to enable localization later on we can always un-ignore those files again.
About adding possible other preprocessors: I'm a little bit hesitant to do this. Right now less and sass seem like a good addition, but with the rise of Tailwind people might expect something there, too, and over time it could become too bloated. I'd like to keep this to TypeScript-only for now. Maybe we should instead switch how we deal with these diagnostic errors and ignore errors that come from missing modules if there's no svelte.config.js? -> we should probably discuss this in an issue 😄