Token thread_open not supported by Markdown parser.

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GIVEN I have created a markdown cell with some markdown content
WHEN I reload the page
THEN I may be presented with the following error
AND the markdown cell may fail to load / display

Uncaught (in promise) Error: Token type `thead_open` not supported by Markdown parser

This is likely to be related to a previous issue - #82

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I might look into this, are there any development docs / guidelines that I could look into?

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I think this issues will arise if a table is added as markdown content