Fix manifest.json for PWA support

[jag-k]

Why this is happend?

Vite (or SvelteKit) generate manifest.json for... debugging, I think (link to this manifest). This is override existed static/manifest.json file and PWA not working. You can't see this side-effect while developing (using npm run dev), but if you visit real paimon.moe you saw this:

Unavailable Manifest

Why you need PWA?

1. Its so power-full, and I want to using this site like real app. And for me mobile "app" is important too.
2. In iOS 16.4 beta you can use Web Push and Web Notification API ONLY in "Add to Home Screen"-application. Proof of work:

Reminder page with available notifications on iOS	Request for sending notification	Apps and "PWA"-apps

What the fix?

Fix is too simple: rename existed manifest.json. For example: pwa-manifest.json, what I did in this PR.
And in this PR I add some minor fixes, like forgotten await and adding .editorconfig for non-VSCode editors.