fix(vsix-plugin): set mime type in dev mode

[CompuIves]

In dev mode the mime type of the base64 string is hardcoded to text/javascript. This works for most files, but it won't work for e.g. file icons, which are svg. In that case, it will not render anything:

With this change, we use the inferred mime type for the base64. Now the main question is... Will this work for all file types?

[CGNonofr]

Oh well spotted!

What is the issue though? all that mimeType stuff was added because it was important for vite to set the accept header, otherwise it was trying to bundle/compile asset files. But for base64 urls, I'm not sure what can be the issue

[CompuIves]

The main issue is that VSCode injects these base64 URLs as inline images in CSS. If the mimetype is not right, the browser refuses to render the icon.

[CompuIves]

Would it be possible to cut a new release with these changes? That would enable me to do some additional work on the repo where we use the library 😄