Can modified the support for table font alignment render?

[yeshiqing]

As u can see, the colon in the second row demonstrates the style of the font alignment in the column

| left align th|right align th| middle align th|
| :------| ------: | :------: |
|  text  | foo | bar |

But if there are whitespaces on either side of the symbol colon :, the table can't be rendered correctly.

I dived a lot in the source and found this may concerned:"OmniMarkupPreviewer\OmniMarkupLib\Renderers\libs\python3\docutils\parsers\rst\tableparser.py"

I want to improve my work efficiency ~ please do me a favor~