Embeds - Support for formulas

[adrian-moisa]

• Adding support for formulas can be done using one of the available libs for latex formulas. We even have a PR from one contributor but it was not yet merged. I've inspected the code and saw some issues. There was no reply back. We should inspect the code and see if we can find the solutions ourselves. The major complaints are around the dependencies if they can be trusted or not.
• In essence adding support is rather simple, we need to add a new type of embed.
• Ideally the editing of formulas could be dine like in Google drive using a visual formula editor solution. However at the moment there's none in Flutter and us building it from scratch is rather a complex commitment. That could be done only if the VS platform has revenue.
• The next best thing is to use an editor card instead of modal. Similar to how we did the quick menu or the link edit tooltip.
• Setup demo page, write docs and tests

https://katex.org/ https://stackoverflow.com/questions/61771911/how-to-render-latex-in-flutter-offline