fix: multi-page different usage of `filename` and `template`

[ThornWalli]

Hello,

I am currently trying Multi-Entrypoints with multi Page templates.

Unfortunately I found that something is difficult to get running. After I had it then however, I had to determine... That certain things in the Plugin are not correctly assigned.

This is about the two properties template and filename. According to the code there seems to be inconsistencies. When and where the template or filename is accessed, is somewhat inconsistent.

I have expanded the places in this PR, but somehow there seems to be an inconsistency in it.

https://github.com/vbenjs/vite-plugin-html/blob/841d4ef04c3cf5ff0d4339350ae336aa83aa70ed/packages/core/src/htmlPlugin.ts#L297-L299

https://github.com/vbenjs/vite-plugin-html/blob/841d4ef04c3cf5ff0d4339350ae336aa83aa70ed/packages/core/src/htmlPlugin.ts#L322-L346

What is this? If I replace the template there with filename, this then works and copies the HTML files to the root level, where folder structure is needed. https://github.com/vbenjs/vite-plugin-html/blob/841d4ef04c3cf5ff0d4339350ae336aa83aa70ed/packages/core/src/htmlPlugin.ts#L120-L164

---

My Example:

Config

{
  minify: false,
  pages: [
    {
      entry: './main.js',
      filename: 'src/banners/300x250/index.html',
      template: 'banners/300x250/index.html',
      injectOptions: {
        data: {
          title: 'Index'
        }
      }
    },
    {
      entry: './main.js',
      filename: 'src/banners/800x250/index.html',
      template: 'banners/800x250/index.html',
      injectOptions: {
        data: {
          title: 'Index'
        }
      }
    }
  ]
}

1. in dev the redirection to filename is correct. (e.g. http://localhost:3000/banners/300x250/index.html)
2. in the build as long as closeBundle is not adjusted, I get now the output in the build, unfortunately I do not know how to remove the src path in the generated files. (Background: Everything that is programmed is in the src folder).