Fixes: added issue, table, help to commands, task list more like in github

[RARgames]

1. I forgot to add issue, table, help to commands (in the previous PR) so anyone can use it like this:

<MDEditor 
  commands={[...commands.getCommands(), commands.divider, commands.issue, commands.table, commands.help]}
/>

2. Task list - always add unfinished task in the new line
   This is how Github handles it.
   It makes sense, as you add new task, you probably want to finish them in the future (not add them as finished).

[vercel]

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