add PWA support with vite-plugin-pwa, extract manifest to separate file

[AduchiMergen]

No description provided.

[troggy]

TLDR: this PR is strictly an improvement (e.g. caching app assets for offline use is amazing), though PWA is not yet fully usable (e.g. web+stellar links are not working). I'd merge and keep improving further.

Tested on desktop:

🟩 "Install app" badge visible in browser and works
🟩 App assets are cached with service worker and available offline (tested by setting Offline flag in Dev Tools > Application)
🟧 Setting web+stellar protocol handler keeps opening the website, not a PWA installed app. Not great, would love to see if it is fixable at least in theory

Tested on mobile (via loophole HTTPS site):

🟧 No "install app" prompt visible prompt. Can be installed as usual via menu. Not great, but manifest is used
🟩 App assets are cached with service worker and available offline (tested in Airplane mode)
🟥 Cannot set set protocol handler at all. Clicking either "Handle Stellar protocol requests" menu option or prompt on account view screen does nothing.

Testing notes:

Checkout and build for web:

git remote add aduchi git@github.com:AduchiMergen/sunce.git
git fetch aduchi
git checkout aduchi/PWA
npm install
npm run build:web
npx http-server -p 5002 dist

Run with https (in parallel with web part served from localhost:5002):

loophole http --hostname sunce-pwa-test 5002

[troggy]

need to sync package-lock with package.json (npm install will do)

[troggy]

ещё неплохо бы потестить авто-обновление:

1. Пользователь открыл Сунце → ресурсы закэшировались
2. Сунце обновилось
3. Пользователь открывает Сунце → подтягивается последняя версия ресурсов.

Пользователь продолжит работать со старой версией до перезагрузки?

cc @sozidatel

[troggy]

@AduchiMergen порезолвишь конфликты?