Vscode-markdown: when hyphens less then 3, the table formatter not work

[baby5]

|one|two| 
|--|--|
|three|four|

will not format

if table with hyphens less then 3 is invalid, the "preview" should not to render it
it cause confusion

thanks

[yzhang-gh]

Thanks. There was an "at least 3 spaces" requirement before in GFM but it is not now. I will fix it.

[yzhang-gh]

Shiped with v2.0.0