Broaden ODT support

[ferndot]

Summary

ODT.js is growing in its support for the ODT format, but it is still incomplete.

We would love it if you could implement any of the listed missing features, or anything else that is missing.

I am here if you have any questions 😄

Missing Features

Features on which getHTML throws

• Any encoding other than utf-8
• Annotations
• Tracked changes
• Charts

Features on which getHTML doesn't throw

• Various types of images
• Non-"manual" styles
• Unordered lists
• List styles (bullets,)
• Strikethrough
• Underlined text nested inside non-underlined text
• Underline-color
• Loads of other styles