Declare type of Vite plugin on Astro integration

[Fryuni]

• Closes #7

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Comparison is base (e449e6f) 100.00% compared to head (b53b07a) 100.00%.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #9 +/- ## ========================================= Coverage 100.00% 100.00% ========================================= Files 29 29 Lines 1572 1572 Branches 312 312 ========================================= Hits 1572 1572 ```

:umbrella: View full report in Codecov by Sentry.
:loudspeaker: Have feedback on the report? Share it here.

[elringus]

Thanks!