[Astro] inline styles set to `[object Object]` in markdown for local images

[mrkirby153]

Describe the bug
When using the imageService with astro markdown files, the resulting <img> tag generated has its inline styles set to [object Object].

To Reproduce
Steps to reproduce the behavior:

1. Add an image to a markdown file (e.g. ![My Image](./image.jpg)
2. Render the markdown (e.g. via a content collection)
3. Run astro dev or astro build
4. Look at the generated HTML in the dev console

https://stackblitz.com/edit/github-ay3eaawt -- Looking at any of the images on this (/blog/markdown-style-guide/) should demonstrate the issue

Expected behavior
The inline styles should be rendered correctly.

Screenshots