build: migrate from Webpack to Vite

[ShGKme]

• Migrate from Webpack to Vite, including:
  • Using ESBuild
  • Extracting CSS

Metric	Before	After
Build time	16s	9s
main page size	4 MB	1.3 MB JS + 0.01 MB CSS
settings page size	3.7 MB	0.6 MB JS + 0.07 MB CSS
admin-settings page size	3.6 MB	0.5 MB JS + 0.04 MB CSS
total size	6.4 MB	1.4 MB JS + 0.12 MB CSS

[ShGKme]

Checking reuse

[nickvergessen]

Checking reuse

Add css/**.css to https://github.com/nextcloud/notifications/blob/master/REUSE.toml#L15 ?

[ShGKme]

Checking reuse

Add css/**.css to https://github.com/nextcloud/notifications/blob/master/REUSE.toml#L15 ?

Not only. Also .map files in for .mjs and vendor.licenses.txt

[Antreesy]

Smoke tested, works fine. Changes also look valid. Thanks!

[Antreesy]

/backport to stable30