feat: tables support

[shagr4th]

Column alignment is supported, as well as pipe escaping
Should fix Issue #1843

[jxpsert]

This is a much-needed feature. Checks seem to pass, except for the backend ones that haven't run and aren't relevant.
Merging this will greatly improve memos.

[shagr4th]

Actually this is not quite merge-ready, because using a regex is quite limiting to determine the validity of a markdown table expression
Right now, the regex I wrote mandates the use of a starting "|" at the beginning of the header (which is optional in many parsers), and does not check if the headers count and hyphens count is the same (I need to subclass a custom Regexp class and add theses additional checks) : this one could trigger false positives on text content not intended to be in a table.

Also, inserting a wrongly formatted table alongside other tables, breaks some of them (even if they have a correct syntax)

Anyway, it's a good start I think, I'll solve these parsing issues

[shagr4th]

Sorry for the multiple commits, it was more difficult than I thought. Right now, this PR pass most of the formatting tests found in the markdown-it test suite

The ones actually failing are related to backlash and backticks escaping (not supported right now in the parser), but this is not related to this table extension, so maybe for a future PR

[boojack]

LGTM. The syntax of table is really hard to implement with regular. Thanks for your contribution.