E0142: A template file has no package clause, or another package's

A .vuka.html file starts with its package clause, as a Go file does: the package of its directory (or of the directory's external test package, layouts_test, for that package's templates). Comments may come before it; imports, the main markup and the func templates follow it.

vuka fmt adds a missing clause, and vuka fix templates-package adds it to every template file of a module.

Wrong

<!-- layouts/admin.vuka.html -->
<script lang="go">
type Admin struct {
	Children ui.Node
}
</script>

<div class="admin">{Children}</div>

Right

<!-- layouts/admin.vuka.html -->
<script lang="go">
package layouts

import "github.com/vuka-lang/ui/v2"

type Admin struct {
	Children ui.Node
}
</script>

<div class="admin">{Children}</div>