Allow for embedded images in markdown

[cuteiosdev]

Purpose

This will add support for markdown that contains images as a base64 encoded string within the markdown syntax. Typically this is seen like the following:

![Embedded markdown image]("data:image/png;base64,...")

Approach

The approach taken is to mirror what is being done by ImageProvider and InlineImageProvider but to allow for when the source is a string rather than a url

Caveats

Would love some help and feedback on the following to make sure the changes are appropriate

• Adding to demo project
• Unit tests