Readme Plugin: add support to loading images in readme

### Describe the feature

At the moment, when the readme.md file has an image, it doesn't load correctly in the backstage plugin, it only loads in GitHub.
This request is about adding images support to the readme backstage plugin.

### Added value

There is currently no workaround, unfortunately the image loads as a broken file (screenshot below). We rely heavily on having images and diagrams in the readme of the repos.

### Additional context
the code of the md file looks like this:
```
# Testing

refersh pls

```

The plugin is rendered like this: