GFM Tables don't seem to tokenize column alignment

[boswelja]

GitHub-flavored Markdown adds support for tables, which support setting column alignment. However, I don't see anything that the parser gives us to handle different alignments. For example, the following table with alignments

| foo | bar | baz |
| :--- | ---: | :---: |

Gives us the same ASTNode tree as the following table with no alignments

| foo | bar | baz |
| --- | --- | --- |

See https://docs.github.com/en/get-started/writing-on-github/working-with-advanced-formatting/organizing-information-with-tables#formatting-content-within-your-table for alignment information.