fix: `push-manifest.json` CSS asset type

[rschristian]

What kind of change does this PR introduce?

bugfix

Did you add tests for your changes?

No

Summary

Bug introduced by typo in #1680

I believe this is more of a theoretical bug than a real issue at this time. Our test suite ensures everything is working as intended in the basic situations at least:

https://github.com/preactjs/preact-cli/blob/6aba5d8e4c165c81f258ca9f367fea6c9a08cf17/packages/cli/tests/images/build.js#L219-L237

In order to handle async chunks generated by Webpack, we loop through the chunks and assign types accordingly. We don't skip the main route chunks while doing so despite them already being set (~~which maybe we should correct but not really important either way~~ did it), so this corrected for the wrong type being set:

https://github.com/preactjs/preact-cli/blob/6aba5d8e4c165c81f258ca9f367fea6c9a08cf17/packages/cli/lib/lib/webpack/create-load-manifest.js#L52-L56

Does this PR introduce a breaking change?

No

[changeset-bot[bot]]

🦋 Changeset detected

Latest commit: 7723a12446c44d6ffbe30002cad9b2e13fb087a7

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 1 package

Name	Type
preact-cli	Patch

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